Polyisobutylene-based polyurethanes

ABSTRACT

An elastomeric polymer, comprising ( 1 ) a hard segment in the amount of 10% to 60% by weight of the elastomeric polymer, wherein the hard segment includes a urethane, urea or urethaneurea; and ( 2 ) a soft segment in the amount of 40% to 90% by weight of the elastomeric polymer. The soft segment comprises (a) at least 2% by weight of the soft segment of at least one polyether macrodiol, and/or at least one polycarbonate macrodiol; and (b) at least 2% by weight of the soft segment of at least one polyisobutylene macrodiol and/or diamine.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/685,858, filed Jan. 12, 2010, which claims the benefit of U.S.Provisional Application No. 61/204,856, filed on Jan. 12, 2009, U.S.Provisional Application No. 61/211,310, filed on Mar. 26, 2009, and U.S.Provisional Application No. 61/279,629, filed on Oct. 23, 2009, all ofwhich are herein incorporated by reference in their entirety.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made subject to a joint research agreementbetween Boston Scientific Corporation and the University ofMassachusetts Lowell. Cardiac Pacemakers, Inc. is a wholly-ownedsubsidiary of Boston Scientific Corporation.

BACKGROUND

Thermoplastic polyurethanes, polyureas and polyurethaneureas representan important family of segmented block copolymer thermoplasticelastomers. They can be extruded, injection or compression molded orsolution spun. They offer a broad range of physical properties andcharacteristics, including high tensile and tear strength, chemical andabrasion resistance, good processibility, and protective barrierproperties. Depending on composition, i.e. on the volume fraction of thesoft, elastomeric segments, these polymers can be soft, rubbery or hardand rigid materials. The hard segments of polyurethanes are composed ofdiisocyanate and a small molecule diol chain extender, while the softsegments are mostly low molecular weight polymeric diols. Similarly,polyureas or polyurethaneureas comprise diamines and a combination ofdiols and diamines, respectively, in addition to diisocyanate. Polymericdiols include polyester diols, polyether diols, and polydiene diols. Thepolyester component is prone to hydrolytic degradation, the polyethercomponent does not have sufficient resistance to oxidative degradation,especially in vivo, and polydienes suffer from inadequate thermal andoxidative stability.

Polyurethanes are the most commonly used materials in the production ofbiomedical devices that come in contact with blood such as pacemakers,defibrillators, angioplasty balloons, surgical drains, dialysis devices,etc. However, polyurethanes generally exhibit insufficient long-term invivo biostability due to oxidation of the polyether soft segment,especially when in contact with metals, which catalyze oxidativedegradation. This deficiency, limits the use of polyurethanes forlong-term applications.

(PIB)-based thermoplastic polyurethanes (TPUs) offer high thermal,oxidative, and hydrolytic stability, however, polyisobutylenepolyurethanes exhibit insufficient mechanical properties.

SUMMARY

Example 1 is a polyurethane or polyurea polymer including a hard segmentand a soft segment. The hard segment is in an amount of 10% to 60% byweight of the polymer. The hard segment includes at least one of aurethane, a urea, or a urethane urea. The soft segment is in an amountof 40% to 90% by weight of the polymer. The soft segment includes atleast one polycarbonate macrodiol and at least one of a polyisobutylenemacrodiol and a polyisobutylene diamine. The at least one polycarbonatemacrodiol is in the amount of 10% to 90% by weight of the soft segment.The at least one of the polyisobutylene macrodiol and thepolyisobutylene diamine is in amount of 10% to 90% by weight of the softsegment. The number average molecular weight of the polymer is greaterthan or equal to 40 kilodaltons.

Example 2 is the polymer of Example 1, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is of aformula:

Each X is independently —OH, —NH₂ or —NHR₄. R_(I) is an initiatorresidue. R₂ and R₃ and R₄ is each independently a C1-C16 alkyl, a C3-C16cycloalkyl, a C2-C16 alkenyl, a C3-C 16 cycloalkenyl, or a C6-C 18 aryl.For each occurrence, R₂ or R₃ is, independently, optionally substitutedwith one or more groups selected from halo, cyano, nitro, dialkylamino,trialkylamino, C1-C16 alkoxy and C1-C16 haloalkyl. n and m are each,independently, integers from 1 to 500.

Example 3 is the polymer of Example 1, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine ishydroxyallyl telechelic polyisobutylene.

Example 4 is the polymer of Example 1, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine ishydroxyalkyl telechelic polyisobutylene.

Example 5 is the polymer of Example 4, wherein the hydroxyalkyltelechelic polyisobutylene is hydroxypropyl telechelic polyisobutylene.

Example 6 is thepolymer of Example 1, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is apolyisobutylene macrodiol and the number average molecular weight of thepolyisobutylene macrodiol is about 400 Da to about 6000 Da.

Example 7 is the polymer of Example 1, wherein the at least onepolycarbonate macrodiol includes at least one poly(alkylene carbonate).

Example 8 is the polymer of Example 1, wherein the hard segment furtherincludes a diisocyanate residue and a chain extender.

Example 9 is the polymer of Example 8, wherein the diisocyanate is4,4′-methylenephenyl diisocyanate and wherein the chain extender is1,4-butanediol.

Example 10 is the polymer of Example 1, wherein the polyisobutylenemacrodiol of the soft segment comprises a hydroxylalkyl telechelicpolyisobutylene residue, and the hard segment comprises a4,4′-methylenediphenyl diisocyanate and 1,4-butanediol chain extender.

Example 11 is the polymer of Example 1, wherein the at least onepolycarbonate macrodiol is in an amount of 10% to 30% by weight of thesoft segment, and the at least one of the polyisobutylene macrodiol andthe polyisobutylene diamine is in an amount of 70% to 90% by weight ofthe soft segment.

Example 12 is a medical device including a polyurethane or polyureapolymer. The polymer includes a hard segment and a soft segment. Thehard segment is in an amount of 10% to 60% by weight of the polymer. Thehard segment includes at least one of a urethane, a urea, or a urethaneurea. The soft segment is in an amount of 40% to 90% by weight of thepolymer. The soft segment includes at least one polycarbonate macrodioland at least one of a polyisobutylene macrodiol and a polyisobutylenediamine. The at least one polycarbonate macrodiol is in the amount of10% to 90% by weight of the soft segment. The at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is in amountof 10% to 90% by weight of the soft segment. The number averagemolecular weight of the polymer is greater than or equal to 40kilodaltons.

Example 13 is the medical device of Example 12, wherein the medicaldevice is selected from the group consisting of a cardiac pacemaker, adefibrillator, a catheter, an implantable prosthesis, a cardiac assistdevice, an artificial organ, a pacemaker lead, a defibrillator lead, ablood pump, a balloon pump, an AV shunt, a biosensor, a membrane forcell encapsulation, a drug delivery device, a wound dressing, anartificial joint, an orthopedic implant or a soft tissue replacement.

Example 14 is a method for preparing a polyurethane or polyurea polymer.The method includes reacting a diisocyanate with a mixture that includesat least one polyisobutylene macrodiol and/or diamine, and at least onepolycarbonate macrodiol, to form a prepolymer having terminally reactivediisocyanate groups; and reacting the prepolymer with a chain extenderto yield the polymer, wherein the polymer includes a hard segment and asoft segment. The hard segment is in an amount of 10% to 60% by weightof the polymer. The hard segment includes at least one of a urethane, aurea, or a urethane urea. The soft segment is in an amount of 40% to 90%by weight of the polymer. The soft segment includes at least onepolycarbonate macrodiol and at least one of a polyisobutylene macrodioland a polyisobutylene diamine. The at least one polycarbonate macrodiolis in the amount of 10% to 90% by weight of the soft segment. The atleast one of the polyisobutylene macrodiol and the polyisobutylenediamine is in amount of 10% to 90% by weight of the soft segment. Thenumber average molecular weight of the polymer is greater than or equalto 40 kilodaltons.

Example 15 is the method of Example 14, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is of formula:

Each X is independently —OH, —NH₂ or —NHR₄. R_(I) is an initiatorresidue. R₂ and R₃ and R₄ is each independently a C1-C16 alkyl, a C3-C16cycloalkyl, a C2-C16 alkenyl, a C3-C 16 cycloalkenyl, or a C6-C 18 aryl.For each occurrence, R₂ or R₃ is, independently, optionally substitutedwith one or more groups selected from halo, cyano, nitro, dialkylamino,trialkylamino, C1-C16 alkoxy and C1-C16 haloalkyl. n and m are each,independently, integers from 1 to 500.

Example 16 is the method of Example 14, wherein the at least onepolycarbonate macrodiol includes at least one poly(alkylene carbonate).

Example 17 is the method of Example 14, wherein the chain extenderincludes at least one member of the group consisting of 1,4-butanediol;1,5-pentanediol; 1,6-hexanediol; 1,8-octanediol; 1,9-nonanediol;1,10-decanediol, 1,12-dodecanediol; 1,4-cyclohexane dimethanol;p-xyleneglycol and 1,4-bis(2-hydroxyethoxy) benzene.

Example 18 is the method of Example 14, wherein the chain extenderincludes at least one member of the group consisting of1,4-diaminobutane; 1,5-diaminopentane; 1,6-diaminohexane;1,8-diaminooctane; 1,9-diaminononane; 1,10-diamonodecane,1,12-diaminododacane; 1,4-diaminocyclohexane; 2,5-diaminoxylene andisophoronediamine and water.

Example 19 is the method of Example 14, wherein the at least onepolycarbonate macrodiol is in an amount of 10% to 30% by weight of thesoft segment, and the at least one of the polyisobutylene macrodiol andthe polyisobutylene diamine is in an amount of 70% to 90% by weight ofthe soft segment.

Example 20 is the method of Example 14, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is apolyisobutylene macrodiol and the number average molecular weight of thepolyisobutylene macrodiol is about 400 Da to about 6000 Da.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingembodiments of the present invention.

FIG. 1 is a schematic diagram of an example of a synthetic procedureemployed to produce the polyisobutylene-containing thermoplasticpolyurethanes that can be employed by the present invention.

FIG. 2 is a schematic diagram of an example of a synthetic procedureemployed to produce the polyisobutylene/polyether-containing thermalpolyurethanes of the present invention.

FIG. 3 is a bar plot showing the ultimate tensile strength (UTS) valuesof eight sample thermal polyurethane polymers of the present invention.

FIG. 4 is a bar plot showing the elongation at break values of eightsample thermal polyurethane polymers of the present invention.

FIG. 5 is a schematic diagram of an example of a synthetic procedureemployed by the present invention to produce polyurethaneureas based onPIB and PTMO segment.

FIG. 6 is a representative FTIR spectrum of 60A 82 PIB-PTMOpolyurethanes of the present invention.

FIG. 7 is a FTIR spectrum of Pellethane™ P55D.

FIG. 8 is a plot of the weight loss of various PIB-PTMO polyurethanes asa function of time of the present invention.

FIG. 9 is a plot of the weight loss of various PIB-PTMO polyurethanes ofthe present invention at 12 weeks as a function of PTMO content.

FIG. 10 is a plot of tensile strength of various PIB-PTMO polyurethanesof the present invention as a percentage of the original untreatedsample as a function of time.

FIG. 11 is an a Gas Permeation Chromatography (GPC)/Refractive Index(RI) detection profile of a PIB-PTMO polyurethane sample of the presentinvention, “Sat 60A91”. The elution time is indicated in minutes.

FIG. 12 is a GPC/RI profile of Pellethane™ P80A shown for comparisonwith the profile of “Sat 60A91” of FIG. 11.

FIG. 13 depicts SEM pictures of Pellethane™ P55D taken at 300×magnification.

FIG. 14 depicts SEM pictures of PIB-PTMO polyurethane sample of thepresent invention, “80A 73” at 300× magnification.

FIG. 15 depicts SEM pictures of PIB-PTMO polyurethane sample of thepresent invention, “80A 82” at 300× magnification.

FIG. 16 depicts SEM pictures of PIB-PTMO polyurethane sample of thepresent invention, “80A 91” at 300× magnification.

DETAILED DESCRIPTION Glossary

As used herein, the term “polydispersity index” (PDI) means is a measureof the distribution of molecular mass in a given polymer sample. The PDIcalculated is the weight average molecular weight divided by the numberaverage molecular weight.

As used herein, the term “macrodiol” means a polymeric diol. Examplesinclude polyether compounds of formula

HO—[CH(R)—(CH₂)_(k)—O]_(I)—H,   (I)

-   -   and polyisobutylene polymers of formula

Values and preferred values for the variables in formulas (I) and (II)are defined below.

Similarly, the phrase “macrodiol and/or diamine” is used, the referenceis being made to a polymeric diamine similar in structure to the diolsof formula (II), in which the terminal hydroxyl groiups are replacedwith amino or alkylaminogroups, as defined below.

As used herein, the term “telechelic”, when referring to a polymer,means a polymer carrying functionalized endgroups. Examples oftelechelic polymers are difunctional polymers of formulas (I) and (II),above. Telechelic polymers can be used, e.g., for the synthesis of blockco-polymers.

As used herein, the term “BDO” refers to 1,4-butanediol.

As used herein, the term “MDI” refers to4,4′-methylenebis(phenylisocyanate).

As used herein, the term “PTMO” refers to polytetramethylene oxide.

As used herein, the term “PlB” means a polyisobutylene, i.e. a compoundformed by polymerization of an optionally substituted butadiene.

As used herein, the term “TPU” means a thermoplastic polyurethane.

As used herein, the term “PIB-TPU” means a polyisobutylene-basedthermoplastic polyurethane obtained by any known process. The termincludes the elastomeric polyurethanes materials described herein.

As used herein, the term “PIB-PTMO-TPU” means a polyisobutylene-based,polytetramethylene oxide-containing thermoplastic polyurethane obtainedby any known process and includes the elastomeric polyurethanesmaterials described herein.

As used herein, the term “initiator residue” refers to a difunctionalchemical moiety, that links two linear chains of a polymer. For example,in a polyisobutylene polymer of formula

where values and preferred values for the variables are defined below,R₁ is an initiator residue. Examples of initiator residues includedicumyl and 5-tert-butyl-1,3 dicumyl that correspond to dicumylchloride, methylether or ester, respectively, are used as initiator.Other examples include 2,4,4,6-tetramethylheptylene or2,5-dimethylhexylene, which arise when2,6-dichloro-2,4,4,6-tetramethylheptane or2,5-dichloro-2,5-dimethylhexane is used as initiator. Many othercationic mono- and multifunctional initiators are known in the art.

Definitions of Terms

The term “alkyl”, as used herein, unless otherwise indicated, meansstraight or branched saturated monovalent hydrocarbon radicals offormula C_(n)H_(2n+1). In some embodiments, n is from 1 to 18. In otherembodiments, n is from 1 to 12. Preferably, n is from 1 to 6. In someembodiments, n is 1-1000, for example, n is 1-100. Alkyl can optionallybe substituted with —OH, —SH, halogen, amino, cyano, nitro, a C1-C12alkyl, C1-C12 haloalkyl, C1-C12 alkoxy, C1-C12 haloalkoxy or C1-C12alkyl sulfanyl. In some embodiments, alkyl can optionally be substitutedwith one or more halogen, hydroxyl, C1-C12 alkyl, C2-C12 alkenyl orC2-C12 alkynyl group, C1-C12 alkoxy, or C1-C12 haloalkyl. The term alkylcan also refer to cycloalkyl.

The term “cycloalkyl”, as used herein, means saturated cyclichydrocarbons, i.e. compounds where all ring atoms are carbons. In someembodiments, a cycloalkyl comprises from 3 to 18 carbons. Preferably, acycloalkyl comprises from 3 to 6 carbons. Examples of cycloalkylinclude, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, and cycloheptyl. In some embodiments, cycloalkyl canoptionally be substituted with one or more halogen, hydroxyl, C1-C12alkyl, C2-C12 alkenyl or C2-C12 alkynyl group, C1-C12 alkoxy, or C1-C12haloalkyl.

The term “haloalkyl”, as used herein, includes an alkyl substituted withone or more F, Cl, Br, or I, wherein alkyl is defined above.

The terms “alkoxy”, as used herein, means an “alkyl-O—” group, whereinalkyl is defined above. Examples of alkoxy group include methoxy orethoxy groups.

The term “aryl”, as used herein, refers to a carbocyclic aromatic group.Preferably, an aryl comprises from 6 to 18 carbons. Examples of arylgroups include, but are not limited to phenyl and naphthyl. Examples ofaryl groups include optionally substituted groups such as phenyl,biphenyl, naphthyl, phenanthryl, anthracenyl, pyrenyl, fluoranthyl orfluorenyl. An aryl can be optionally substituted. Examples of suitablesubstituents on an aryl include halogen, hydroxyl, C1-C12 alkyl, C2-C12alkene or C2-C12 alkyne, C3-C12 cycloalkyl, C1-C12 haloalkyl, C1-C12alkoxy, aryloxy, arylamino or aryl group.

The term “aryloxy”, as used herein, means an “aryl-O—” group, whereinaryl is defined above. Examples of an aryloxy group include phenoxy ornaphthoxy groups.

The term arylamine, as used herein, means an “aryl-NH—”, an“aryl-N(alkyl)-”, or an “(aryl)₂-N—” groups, wherein aryl and alkyl aredefined above.

The term “heteroaryl”, as used herein, refers to aromatic groupscontaining one or more heteroatoms (O, S, or N). A heteroaryl group canbe monocyclic or polycyclic, e.g. a monocyclic heteroaryl ring fused toone or more carbocyclic aromatic groups or other monocyclic heteroarylgroups. The heteroaryl groups of this invention can also include ringsystems substituted with one or more oxo moieties. Examples ofheteroaryl groups include, but are not limited to, pyridinyl,pyridazinyl, imidazolyl, pyrimidinyl, pyrazolyl, triazolyl, pyrazinyl,quinolyl, isoquinolyl, tetrazolyl, furyl, thienyl, isoxazolyl,thiazolyl, oxazolyl, isothiazolyl, pyrrolyl, quinolinyl, isoquinolinyl,indolyl, benzimidazolyl, benzofuranyl, cinnolinyl, indazolyl,indolizinyl, phthalazinyl, pyridazinyl, triazinyl, isoindolyl, purinyl,oxadiazolyl, thiazolyl, thiadiazolyl, furazanyl, benzofurazanyl,benzothiophenyl, benzotriazolyl, benzothiazolyl, benzoxazolyl,quinazolinyl, quinoxalinyl, naphthyridinyl, dihydroquinolyl,tetrahydroquinolyl, dihydroisoquinolyl, tetrahydroisoquinolyl,benzofuryl, furopyridinyl, pyrolopyrimidinyl, and azaindolyl.

The foregoing heteroaryl groups may be C-attached or N-attached (wheresuch is possible). For instance, a group derived from pyrrole may bepyrrol-1-yl (N-attached) or pyrrol-3-yl (C-attached).

Suitable substituents for heteroaryl are as defined above with respectto aryl group.

Suitable substituents for an alkyl, cycloalkyl include a halogen, analkyl, an alkenyl, a cycloalkyl, a cycloalkenyl, an aryl, a heteroaryl,a haloalkyl, cyano, nitro, haloalkoxy.

Further examples of suitable substituents for a substitutable carbonatom in an aryl, a heteroaryl, alkyl or cycloalkyl include but are notlimited to —OH, halogen (—F, —Cl, —Br, and —I), —R, —OR, —CH₂R, —CH₂OR,—CH₂CH₂OR,. Each R is independently an alkyl group.

In some embodiments, suitable substituents for a substitutable carbonatom in an aryl, a heteroaryl or an aryl portion of an arylalkenylinclude halogen, hydroxyl, C1-C12 alkyl, C2-C12 alkenyl or C2-C12alkynyl group, C1-C12 alkoxy, aryloxy group, arylamino group and C1-C12haloalkyl.

In addition, the above-mentioned groups may also be substituted with ═O,═S, ═N-alkyl.

In the context of the present invention, an amino group may be a primary(—NH₂), secondary (—NHR_(p)), or tertiary (—NR_(p)R_(q)), wherein R_(p)and R_(q) may be any of the alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl,cycloalkoxy, aryl, heteroaryl, and a bicyclic carbocyclic group. A(di)alkylamino group is an instance of an amino group substituted withone or two alkyls.

A trialkylamino group is a group —N⁺(R_(t))₃, wherein R_(t) is an alkyl,as defined above.

Polyurethanes and Polyureas

As used herein, a “polyurethane” is any polymer consisting of a chain oforganic units joined by urethane (carbamate, —NH—COO—) links.Polyurethane polymers can be formed by reacting a molecules containingat least two isocyanate functional groups with another moleculecontaining at least two alcohol (hydroxyl) groups. By reacting anisocyanate group, —N═C═O, with a hydroxyl group, —OH, a urethane linkageis produced. A catalyst can be used. Similarly, in polyureas the linksare urea groups (—NH—CO—NH—) that are obtained by reacting an isocyanategroup with an amine group —NH₂.

For example, polyurethanes can be produced by the polyaddition reactionof a polyisocyanate with a polyalcohol (a polyol, an example of which isa macrodiol). The reaction mixture can include other additives. Apolyisocyanate is a molecule with two or more isocyanate functionalgroups, R¹—(N═C═O)_(n≧2) and a polyol is a molecule with two or morehydroxyl functional groups, R²—(OH)_(n≧2). R¹ and R² are eachindependently an aliphatic or an aromatic moiety. The reaction productis a polymer containing the urethane linkage, —R¹NHCOOR²—.

Polyisocyanate that contain two isocyanate groups are calleddiisocyanates. Isocyanates can be aromatic, such as diphenylmethanediisocyanate (MDI) or toluene diisocyanate (TDI); or aliphatic, such ashexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI). Anexample of an isocyanate is polymeric diphenylmethane diisocyanate,which is a blend of molecules with two-, three-, and four- or moreisocyanate groups, with an average functionality of 2.7.

Polyols that contain two hydroxyl groups are called macrodiols, thosewith three hydroxyl groups are called macrotriols. Examples of polyolsinclude polycarbonate polyols, polycaprolactone polyols, polybutadienepolyols, and polysulfide polyols.

Additive such as catalysts, surfactants, blowing agents, cross linkers,flame retardants, light stabilizers, and fillers are used to control andmodify the reaction process and performance characteristics of thepolymer.

Examples of aromatic isocyanates are toluene diisocyanate (TDI) anddiphenylmethane diisocyanate (MDI). TDI consists of a mixture of the2,4- and 2,6-diisocyanatotoluene isomers. Another example of an aromaticisocyanate is TDI-80 (TD-80), consisting of 80% of the 2,4-isomer and20% of the 2,6-isomer.

Examples of aliphatic (including cycloaliphatic) isocyanates are1,6-hexamethylene diisocyanate (HDI),1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophoronediisocyanate, IPDI), and 4,4′-diisocyanato dicyclohexylmethane (H₁₂MDI).Other aliphatic isocyanates include cyclohexane diisocyanate (CHDI),tetramethylxylene diisocyanate (TMXDI), and1,3-bis(isocyanatomethyl)cyclohexane (H₆XDI).

Chain extenders (f=2) and cross linkers (f=3 or greater) are lowmolecular weight hydroxyl and amine terminated compounds that play animportant role in the polymer morphology of polyurethane fibers,elastomers, adhesives, and certain integral skin and microcellularfoams. Examples of chain extenders and cross linkers are ethylene glycol(EG), 1,4-butanediol (BDO), diethylene glycol (DEG), glycerine, andtrimethylol propane (TMP).

The elastomeric properties of polyurethanes, polyureas andpolyurethaneureas are derived from the phase separation of the “hardsegment” and the “soft segment” domains of the polymer chain. Forexample, hard segments that comprise urethane units can serve ascross-links between the soft segments that comprise polyol (e.g.,macrodiol) units (e.g., polyisobutane diols, polyether diols, and/orpolyester diols). Without being limited to any particular theory, it isbelieved that the phase separation occurs because the mainly non-polar,low melting soft segments are incompatible with the polar, high meltinghard segments. The polyol-containing soft segments are mobile and arenormally present in coiled formation, while the isocyanate-containinghard segments (which can also include chain extenders) are stiff andimmobile. Because the hard segments are covalently coupled to the softsegments, they inhibit plastic flow of the polymer chains, thus creatingelastomeric resiliency. Upon mechanical deformation, a portion of thesoft segments are stressed by uncoiling, and the hard segments becomealigned in the stress direction. This reorientation of the hard segmentsand consequent powerful hydrogen bonding contributes to high tensilestrength, elongation, and tear resistance values.

Although the synthesis of polyurethanes is usually presented asproceeding via formation of urethane (carbamate) linkages by thereaction of isocyanates and alocohols, this is an oversimplification.See, for example, G. ODIAN: PRINCIPLES OF POLYMERIZATION, FOURTH ED.Wiley Interscience, 2004. Accordingly, it is more convenient to definethe polyurethane compositions via weight percent of the componentsrather than structurally.

Accordingly, in some embodiments, the present invention is anelastomeric polymer, comprising (1) a hard segment in the amount of 10%to 60% by weight of the elastomeric polymer, wherein the hard segmentincludes a urethane, urea or urethaneurea; and (2) a soft segment in theamount of 40% to 90% by weight of the elastomeric polymer. The softsegment comprises at least 2% by weight of the soft segment of at leastone polyether macrodiol, and/or at least one polycarbonate macrodiol andat least 2% by weight of the soft segment of at least onepolyisobutylene macrodiol and/or diamine.

In certain embodiments, the number average molecular weight of theelastomeric polymer is not less than about 40 kilodaltons (kDa). Inother embodiments, the number average molecular weight of theelastomeric polymer is not less than about 50 kilodaltons. Inalternative embodiments, wherein the number average molecular weight ofthe elastomeric polymer is not less than about 60 kDa, not less thanabout 70 kDa, not less than about 80 kDa, not less than about 90 kDa,not less than about 100 kDa, not less than about 110 kDa, not less thanabout 120 kDa, not less tha about 130 kDa, not less than about 140 kDaor not less tha about 150 kDa.

In certain embodiments, the hard segment can be present in the amount of15, 20, 25, 30, 35, 40, 45, 50, or 55%.

In certain embodiments, soft segment is present in the amount of 45, 50,55, 60, 65, 70, 75, 80, or 85%. Polyether and/or polycarbonate can bepresent in the amount of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60,65, 70, 75, 80 or 85%. Polyisobutylene can be present in the amount of5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85%.

One of ordinary skill can easily determine a suitable polyethermacrodiol. Preferably, at least one polyether macrodiol is a compound offormula

HO—[CH(R)—(CH₂)_(k)—O]_(I)—H,

wherein R, for each occurrence, is independently a C1-C12 alkyl or —H; kis an integer not less than 1; and I is an integer not less than 1.

One of ordinary skill can easily determine a suitable polyisobutylenemacrodiol or diamine. Preferably, at least one polyisobutylene macrodioland/or diamine is of formula:

wherein each X is independently —OH, —NH₂ or —NHR₄, and wherein R₁ is aninitiator residue (defined above). R₂, R₃ and R₄ is each independently aC1-C16 alkyl, a C3-C16 cycloalkyl, a C2-C16 alkenyl, a C3-C16cycloalkenyl, a C2-C16 alkynyl, a C3-C16 cycloalkynyl, or a C6-C18 aryl,wherein, for each occurrence, R₂ or R₃ is, independently, optionallysubstituted with one or more groups selected from halo, cyano, nitro,dialkylamino, trialkylamino, C1-C16 alkoxy and C1-C16 haloalkyl.Integers n and m are each, independently, from 1 to 500.

Preferably, the polyisobutylene macrodiol or diamine is hydroxy or aminoallyl telechelic polyisobutylene. In one embodiment, the molecularweight of at least one polyisobutylene macrodiol or diamine is about 400Da to about 6000 Da. For example, polyisobutylene macrodiol or diamineis about 500, 1000, 2000, 3000, 4000, or 5000 Da. In certainembodiments, the molecular weight of at least one polyisobutylenemacrodiol or diamine is about 1000 Da to about 3000 Da. For example, themolecular weight of at least one polyisobutylene macrodiol or diamine isabout 1000, 1500, 2000, or 2500 Da.

In preferred embodiments, R₂ and R₃ is each independently a moietyselected from —CH₂—CH═CH—CH₂—, —CH₂—CH₂—CH₂—CH₂—, —CH₂—CH₂—CH₂—, and—CH₂—CH(CH₃)—CH₂—.

In one embodiment, the elastomeric polymer of the present inventioncomprises a soft segment that includes at least one polyether macrodioland at least one polycarbonate macrodiol; and at least 2% by weight ofthe soft segment of the at least one polyisobutylene macrodiol, and/ordiamine.

In another embodiment, the elastomeric polymer of the present inventioncomprises a soft segment that includes: (a) about 10% to about 90% byweight of the soft segment of the at least one polyisobutylenemacrodiol, and/or diamine; and (b) eitherabout 10% to about 90% byweight of the soft segment of the at least one polyether macrodiol, orabout 10% to about 90% by weight of the soft segment of the at least onepolycarbonate macrodiol, or about 10% to about 90% by weight of the softsegment of the at least one polyether macrodiol and the at least onepolycarbonate macrodiol.

For example, the soft segment can include from about 10% to about 30% byweight of the soft segment of at least one polycarbonate macrodiol. Forexample, the soft segment can include at least one polycarbonatemacrodiol in the amount of 15, 20 or 25%. Alternatively, the softsegment can include from about 10% to about 30% by weight of the softsegment of the at least one polyether macrodiol and the at least onepolycarbonate macrodiol. For example, the soft segment can include atleast one polyether macrodiol and the at least one polycarbonatemacrodiol in the amount of 15, 20 or 25%.

In one embodiment, the soft segment can include from about 10% to about30% by weight of the soft segment of the at least one polyethermacrodiol. For example, the soft segment can include at least onepolyether macrodiol in the amount of 15, 20 or 25%.

In another embodiment, the soft segment includes from about 10% to about90% by weight of the soft segment of the at least one polyisobutylenemacrodiol, and/or diamine. For example, the soft segment can include atleast one polyisobutylene macrodiol, and/or diamine in the amount of 20,30, 40, 50, 60, 70 or 80%.

In a further embodiment, the soft segment can include from about 70% toabout 90% by weight of the soft segment of the at least onepolyisobutylene macrodiol, and/or diamine. For example, the soft segmentcan include at least one polyisobutylene macrodiol, and/or diamine inthe amount of 70, 75, 80 or 85%.

Preferably, at least one polyether macrodiol includes at least onemember selected form the group consisting of poly(ethylene oxide) diol,poly(propylene oxide) diol, poly(trimethylene oxide) diol,poly(tetramethylene oxide) diol, poly(hexamethylene oxide) diol,poly(heptamethylene oxide) diol, poly(octamethylene oxide) diol andpoly(decamethylene oxide) diol.

One of ordinary skill in the art will be able to easily determine asuitable polycarbonate macrodiol. Preferably, at least one polycarbonatemacrodiol includes at least one member selected from the groupconsisting of a poly(alkylene carbonate) of a formula

where R₇ is a hydrogen, a C1-C12 straight or branched alkyl, or a C3-C12cycloalkyl, q is an integer greater than 1 and p is an integer greaterthan 2. Preferably, R₇ is a hydrogen. Examples of poly(alkylenecarbonate) include poly(tetramethylene carbonate) diol,poly(pentamethylene carbonate) diol, poly(hexamethylene carbonate) diol,or copolymers of thereof.

In certain embodiments, the elastomeric polymer of the present inventioncomprises a hard segment present in the amount of from about 30% toabout 50% by weight of the elastomeric polymer. For example, the hardsegment present in the amount of 35, 40, or 45%.

Examples of the hard segments include the hard segments formed byreacting a diisocyanate with a chain extender. One of ordinary skill inthe art will easily determine a suitable diisocyanate or a chainextender. The diisocyanate can be at least one member selected from thegroup consisting of 4,4′-methylenephenyl diisocyanate; methylenediisocyanate; p-phenylene diisocyanate;cis-cyclohexane-1,4-diisocyanate; trans-cyclohexane-1,4-diisocyanate; amixture of cis cis-cyclohexane-1,4-diisocyanate andtrans-cyclohexane-1,4-diisocyanate; 1,6-hexamethylene diisocyanate;2,4-toluene diisocyanate; cis-2,4-toluene diisocyanate;trans-2,4-toluene diisocyanate; a mixture of cis-2,4-toluenediisocyanate and trans-2,4-toluene diisocyanate; p-tetramethylxylenediisocyanate; and m-tetramethylxylene diisocyanate. The chain extendercan be at least one member selected from the group consisting of1,4-butanediol; 1,5 pentanediol; 1,6-hexanediol; 1,8-octanediol;1,9-nonanediol; 1,10-decanediol, 1,12-dodacanediol; 1,4-cyclohexanedimethanol; p-xyleneglycol and 1,4-bis(2-hydroxyethoxy) benzene.Preferably, the diisocyanate is 4,4′-methylenephenyl diisocyanate andthe chain extender is 1,4-butanediol.

In a preferred embodiment, the polyurethane elastomeric polymer of thepresent invention comprises the soft segment formed from a hydroxyallyltelechelic polyisobutylene and poly(tetramethylene oxide) diol and thehard segment formed from 4,4′-methylenediphenyl diisocyanate and1,4-butanediol.

In another preferred embodiment, the polyurethane elastomeric polymer ofthe present invention comprises the soft segment is derived from ahydroxyallyl telechelic polyisobutylene and poly(hexamethylene oxide)diol and the hard segment is derived from 4,4′-methylenediphenyldiisocyanate and 1,4-butanediol.

In another preferred embodiment, the polyurethane elastomeric polymer ofthe present invention comprises the soft segment formed from (a) ahydroxyallyl difunctional polyisobutylene and (b) poly(tetramethyleneoxide) diol or poly(hexamethylene oxide) diol; and the hard segmentformed from (c) 4,4′-methylenediphenyl diisocyanate and (d)1,4-butanediol.

In certain embodiments, the present invention is an article ofmanufacture comprising any of the polyurethane elastomeric polymersdescribed above. In preferred embodiments, the article is a medicaldevice or an implant. Examples of the article of the present inventioninclude a cardiac pacemaker, a defibrillator, a catheter, an implantableprosthesis, a cardiac assist device, an artificial organ, a pacemakerlead, a defibrillator lead, a blood pump, a balloon pump, an a-V shunt,a biosensor, a membrane for cell encapsulation, a drug delivery device,a wound dressing, an artificial joint, an orthopedic implant or a softtissue replacement. In other embodiments, the article is a fiber, film,engineering plastic, fabric, coating, and adhesive joint.

The methods of synthesis of polyurethane compositions are generally wellknown by one of ordinary skill in the art of polymer chemistry. See, forexample, Gunter Oertel, “Polyurethane Handbook”, 2nd ed. HanserPublishers (1993); or Malcolm P. Stevens, “Polymer Chemistry”, 3d ed.Oxford University Press (1999). The relevant portions of thesepublications are incorporated herein by reference.

The present invention is based, in part, on the discovery of new andimproved methods of polyurethane synthesis. Accordingly, in someembodiments, the present invention is a process for preparing apolyurethane elastomeric polymer. (See FIG. 2 for an example of such aprocedure.) Generally, the process comprises the steps of (a) forming amixture that includes at least one polyisobutylene macrodiol, and/ordiamine, at least one polyether macrodiol and a chain extender; and (b)reacting the mixture with a diisocyanate to yield a polyurethaneelastomeric polymer. Preferably, the elastomeric polymer includes (i) ahard segment in the amount of 10% to 60% by weight of the elastomericpolymer, wherein the hard segment includes a urethane, urea orurethaneurea; and (ii) a soft segment in the amount of 40% to 90% byweight of the elastomeric polymer. Preferably, the soft segment includesat least 2% by weight of the soft segment of at least one polyethermacrodiol, and/or at least one polycarbonate macrodiol, and at least 2%by weight of the soft segment of the at least one polyisobuylenemacrodiol, and/or diamine.

Any one or more of the isocyanates, polyols, chain extenders, or variousadditives can be employed with the synthetic method of the presentinvention. For example, polyether macrodiols and/or polyisobutylenemacrodiol, described above, as well as any mixture thereof, can be usedin the above-described process. Any amounts of the components and theircombinations described above can be used.

Preferably, in the processes of the present invention, the mixture isformed at a temperature of about 45° C. to about 120° C. For example,the mixture is formed at a temperature of about 50, 60, 70, 80, 90, 100or 110° C.

In some embodiments, the mixture is formed in the presence of acatalyst, such as stannous octoate. Other catalysts are well known inthe art and can be used by one of ordinary skill in the art.

In an alternative embodiments, the present invention is a process forpreparing a elastomeric polymer, comprising the steps of (a) reacting adiisocyanate with a mixture that includes at least one polyisobutylenemacrodiol, and/or diamine and at least one polyether macrodiol to form aprepolymer having terminally reactive diisocyanate groups; and (b)reacting the prepolymer with a chain extender to yield a polyurethaneelastomeric polymer. Preferably, the elastomeric polymer includes (i) ahard segment in the amount of 10% to 60% by weight of the elastomericpolymer, wherein the hard segment includes a urethane, urea orurethaneurea; and (ii) a soft segment in the amount of 40% to 90% byweight of the elastomeric polymer. Preferably, the soft segment includesat least 2% by weight of the soft segment of the at least one polyethermacrodiol and/or at least one polycarbonate macrodiol, and at least 2%by weight of the soft segment of the at least one polyisobutylenemacrodiol, and/or diamine.

Any one or more of the isocyanates, polyols, chain extenders, or variousadditives can be employed with the synthetic method of the presentinvention. For example, polyether macrodiols and/or polyisobutylenemacrodiol, described above, as well as any mixture thereof, can be usedin the above-described process. Any amounts of the components and theircombinations described above can be used.

For example, at least one polyether macrodiol employed by theabove-described process is poly(ethylene oxide) diol, poly(propyleneoxide) diol, poly(trimethylene oxide) diol, poly(tetramethylene oxide)diol, poly(hexamethylene oxide) diol, poly(heptamethylene oxide) diol,poly(octamethylene oxide) diol or poly(decamethylene oxide) diol.

Preferably, at least one polycarbonate macrodiol employed by theabove-described process is a poly(alkylene carbonate), as describedabove.

Examples of the chain extenders that can be employed in theabove-described process are 1,4-butanediol; 1,5-pentanediol;1,6-hexanediol; 1,8-octanediol; 1,9-nonanediol; 1,10-decanediol,1,12-dodecanediol; 1,4-cyclohexane dimethanol; p-xyleneglycol and1,4-bis(2-hydroxyethoxy) benzene. Other examples include diamine chainextenders

EXEMPLIFICATION Materials

Sn(Oct)₂ (stannous octoate, Polyscience),4,4′-methylenebis(phenyl-isocyanate) (MDI, Aldrich, 98%), toluene(Aldrich, 99%), chloroform (Aldrich, at least 99.8%), 1,4-butanediol(BDO, Aldrich, 99%), Phthalimide, potassium (Aldrich, 98%), LiBr(Lithium bromide ReagentPlus®, Aldrich, at least 99%), KOH (potassiumhydroxide, Aldrich), Na₂SO₄ (sodium sulfate, Aldrich), Trifluoroaceticacid (TFA, Aldrich), Tetra-n-butylammonium bromide (TBAB, Alfa Aesar, atleast 98%) and Poly(tetramethylene oxide) (PTMO, TERATHANE® 1000polyether glycol, Aldrich) were used as received. Tetrahydrofuran (THF)or toluene were refluxed over sodium metal and benzophenone over nightand distilled under nitrogen atmosphere prior to use. Hexanes werepurified by refluxing over sulfuric acid for 24 hours. They were washedwith aqueous solution of KOH three times followed by distilled water.Then they were stored over sodium sulfate over night at roomtemperature. Finally they were distilled over CaH₂ under nitrogenatmosphere before use.

Measurements

Molecular weights were measured with a Waters HPLC system equipped witha model 510 HPLC pump, model 410 differential refractometer, model 441absorbance detector, on-line multiangle laser light scattering (MALLS)detector (MiniDawn, Wyatt Technology Inc.), Model 712 sample processor,and five Ultrastyragel GPC coulmns connected in the following series:500, 10³, 10⁴, 10⁵, and 100 Å. THF:TBAB (98:2, wt %) was used as acarrier solvent with a flow rate of 1 mL/min. Static tensile properties(Young's modulus, ultimate tensile strength, referred herein as “UTS”,elongation) were measured at room temperature (25° C.) and atmosphericconditions with a 50 N load cell on an Instron Model 4400R at 50 mm/minextension rate. All tests were carried out according to ASTM D412.Samples were cut into dog-bone shape using an ASTM die. All samples werekept at room temperature and atmospheric conditions prior to testing.The polymers were compression molded at 160° C. for 10 min using 17000psi.

Example 1 Preparation of HO-Allyl-Polyisobutylene(PIB)-Allyl-OH

The synthesis of HO-Allyl-PIB-Allyl-OH was carried out by heating theTHF solution of bromoallyl telechelic PIB with aqueous solution of KOHat 130° C. for 3 hours.

For example, Br-Allyl-PIB-Allyl-Br (M_(n)=2200, 50 g, 0.023 mol) wasdissolved in dry THF (1 liter) and a solution of KOH (50 g, 0.9 mol) indistilled water (500 mL) was added to it. The mixture was heated for 3hour at 130° C. in a reactor. The reaction was cooled to roomtemperature. The THF was evaporated using a rotary evaporator. Distilledmethanol (500 mL) was added and the precipitate was allowed to settledown. The precipitate was further dissolved in hexanes (200 mL) andslowly added to methanol (600 mL). The sticky mass was allowed to settledown. The process was repeated two times and the purified polymer wasfinally dried under vacuum at room temperature for 24 hour. Yield: 99%,GPC-MALLS: M_(n)=2400, polydispersity index (PDI)=1.16.

Representative molecular weight data for the hydroxy telechelic PIBs aredescribed in Table 1, below.

TABLE 1 Molecular weight data of the hydroxyallyl telechelic PIBsPolymer M_(n) (NMR) M_(n) (GPC) PDI 1 4200 4300 1.10 2 2200 2400 1.16 31500 1600 1.17

Example 2 Syntheses of Polyisobutylene-Based Thermoplastic Polyurethane(PIB-TPU)

As used in Example 2, the terms “one-step procedure” and “two-stepprocedure” refer to the synthetic scheme exemplified in FIG. 1.

The syntheses of polyurethanes (PUs) with the ratio of soft segment (SS)to hard segment (HS) 80:20 (wt:wt), i.e. PIB(4200)-TPU (Sample CodePIB-TPU-4321), PIB(2200)-TPU (Sample Code PIB-TPU-2211) andPIB(1500)-TPU (Sample Code PIB-TPU-1514) were carried out in tolueneusing MDI and BDO as the chain extender in presence of 1 mol % ofstannous octoate (relative to MDI) at 80° C. The polymers were obtainedby adding MDI as the last reagent (one-step procedure).

One-Step Procedure

For examples, the material PIB-TPU-2211 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 5.2 g, 2.36 mmol) and BDO (212 mg,2.36 mmol) were azeotropically distilled from dry toluene (10 mL). Themixture was kept at 45° C. for 3 hours under vacuum. 25 mL of drytoluene was added to this mixture, followed by Sn(Oct)₂ (20 mg, 0.05mmol) in toluene. The mixture was heated at 80° C. under a slow streamof dry nitrogen gas. MDI (1.24 g, 4.96 mmol) was added to this mixtureand the mixture was stirred vigorously for 6 hours. The mixture wascooled to room temperature, poured into a Teflon® mold and the solventwas evaporated at room temperature in air for 48 hours. Finally thepolymer was dried under vacuum at 50° C. for 12 hours. Representativemolar ratio of the reactants and Shore hardness of the TPUs aredescribed in Table 2.

TABLE 2 Molar ratio of reactants and Shore hardness of PIB TPUHO-Allyl-PIB- MDI/BDO/PIB Wt % Shore Code Allyl-OH (M_(n))¹ (molarratio) SS:HS hardness (A) PIB-TPU- 4200 3/2/1 81:19 60 4321 PIB-TPU-2200 2/1/1 79:21 59 2211 PIB-TPU- 1500 5/1/4 80:20 62 1514 ¹M_(n) ofprecursor HO-Allyl-PIB-Allyl-OH

The M_(n) of PIB-TPU-2211 after various polymerization times is noted inTable 3. The increase in M_(n) was observed till 6 hour time. Thepolyurethane was then cured for one week at room temperature. A furtherincrease in M_(n)=105000, PDI=2.4 was observed for the cured sample.

TABLE 3 Polymerization time and corresponding M_(n) data Polymerizationtime (h) M_(n) (GPC) PDI (GPC)  0¹ 2200 1.16   0.5 23000 1.8   0.7 320001.8 3 66000 2.0 6 87000 2.2 168  105000 2.4 ¹M_(n) of precursorHO-Allyl-PIB-Allyl-OH

The M_(n) of PIB-TPUs having Shore hardness of about 60 A hardnessprepared with polyisobutylenes having different molecular weights aresummarized in Table 4. PIB-TPU-1514 was not soluble in THF:TBAB (98:2 wt%), hence the M_(n) could not be determined.

TABLE 4 GPC data of PIB-TPUs (Shore hardness 60A) Code M_(n) (GPC) PDI(GPC) PIB-TPU-4321 110000 2.3 PIB-TPU-2211 92000 3.1 PIB-TPU-1321 — —

The syntheses of polyurethanes with soft segment (SS) to hard segment(HS) ratio of 60:40 (wt %), e.g. PIB(4200)-TPU (Sample CodePIB-TPU-4761), PIB(2200)-TPU (Sample Code PIB-TPU-2431) andPIB(1500)-TPU (Sample Code PIB-TPU-1321) were carried out by a one-stepsynthetic procedure (see FIG. 1) in toluene using MDI and BDO as thechain extender and 1 mol % of stannous octoate (relative to MDI) ascatalyst at 80° C.

For example, PIB-TPU-2431 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 5.2 g, 2.36 mmol) and BDO (637 mg,7.08 mmol) were azeotropically distilled from dry toluene (10 mL). Themixture was kept at 45° C. for 3 hours under vacuum. 25 mL of drytoluene was added to this mixture, followed by Sn(Oct)₂ (38 mg, 0.09mmol) in toluene. The mixture was heated at 80° C. under a slow streamof dry nitrogen gas. MDI (2.36 g, 9.44 mmol) was added to the mixtureand the mixture was stirred vigorously for 6 hours. The mixture wascooled to room temperature, poured in a Teflon® mold and the solvent wasevaporated at room temperature in air for 48 hours. Finally the polymerwas dried under vacuum at 50° C. for 12 hours.

Representative molar ratio of the reactants and Shore hardness of theTPUs are described in Table 5, below.

TABLE 5 Molar ratio of reactants and Shore hardness of PIB TPUHO-Allyl-PIB- MDI/BDO/PIB Wt % Shore Code Allyl-OH (M_(n)) (molar ratio)SS:HS hardness (A) PIB-TPU- 4200 7/6/1 62:38 81 4761 PIB-TPU- 2200 4/3/160:40 79 2431 PIB-TPU- 1500 3/2/1 59:41 83 1321

The GPC analysis of the TPUs were carried out in THF:TBAB (98:2 wt %).The molecular weight values (Table 6) were obtained in the range of83000-91000 with PDI in the range of 1.8-2.2.

TABLE 6 GPC data of PIB-TPUs (Shore hardness 80A) Code M_(n) (GPC) PDI(GPC) PIB-TPU-4761 87000 2.0 PIB-TPU-2431 91000 2.2 PIB-TPU-1321 830001.8

Representative mechanical property data of the PIB-TPUs are listed inTable 7. The UTS was obtained in the range of 6-9 MPa with elongation atbreak in the range of 40-400%. With an increase in the hard segment tosoft segment ratio, the Young's modulus increased and the elongation atbreak decreased. The thermal processing of TPUs with higher Shorehardness was difficult compared to the softer ones. PIB-TPU-2431 andPIB-TPU-1321 could not be molded into flat sheets for testing, so thetensile properties were not recorded.

TABLE 7 Mechanical property data of PIB-TPUs Young's Tensile ModulusStrength Elongation Polymer Shore (A) (MPa) (MPa) (%) PIB-TPU- 60 6 7200-250 4321 PIB-TPU- 81 40  6 30-40 4761 PIB-TPU- 59 5 9 300-400 2211PIB-TPU- — — — — 2431 PIB-TPU- 62 5 6 100-150 1514 PIB-TPU- — — — — 1321

Changing the catalyst of polymerization from tin octoate to1,3-Diacetoxy-1,1,3,3-tetrabutyldistannoxane (DTDS) the UTS ofPIB-TPU-2211 increased from 9 MPa to 12 MPa and the elongation at breakdecreased to 100% from 350% as shown in Table 8.

TABLE 8 Mechanical property data of the PIB TPUs Young's Tensile ModulusStrength Elongation Polymer Shore A (MPa) (MPa) (%) PIB-TPU-2211 59  5 9 300-400 Sn(Oct)₂ PIB-TPU-2211^(†) 60 24 12 100 DTDS PIB-TPU-2431 — —— — Sn(Oct)₂ PIB-TPU-2431^(†) 80 72 15 30-40 DTDS ^(†)not soluble inTHF/TBAB, soluble in chloroform/TFA

Two-Step Synthesis

In subsequent experiments, the technique for the polyurethane synthesiswas modified by adding 1,4-butanediol (BDO) as the last reagent. Theprocess consisted of two steps. (See FIG. 1.) In the first step,HO-Allyl-PIB-Allyl-OH was mixed with excess of MDI to form theintermediate PUs. In the subsequent step these intermediatepolyurethanes were chain-extended with 1,4-butanediol to obtain the highmolecular weight TPUs. A representative procedure is given below.

The PIB-TPU-4321 was synthesized using the two-step procedure by addingBDO last. HO-Allyl-PIB-Allyl-OH (M_(n)=4200, 5.2 g, 1.24 mmol) wasazeotropically distilled from dry toluene (10 mL). The polymer was keptat 45° C. for 3 hours under vacuum. 25 mL of dry toluene was added tothis mixture, followed by Sn(Oct)₂ (15 mg, 0.037 mmol) in toluene. Themixture was heated at 80° C. under a slow stream of dry nitrogen gas. Toit MDI (930 mg, 3.72 mmol) was added and the mixture was stirredvigorously for 30 min. BDO (223 mg, 2.48 mmol) was added to this mixtureand stirring continued for 4 hours. The mixture was cooled to roomtemperature, poured in a Teflon® mold and the solvent was evaporated atroom temperature in air for 48 hours. Finally the polymer was driedunder vacuum at 50° C. for 12 hours.

As can be seen in Table 9, a higher molecular weight with narrowmolecular weight distribution was observed for the polymer obtained bytwo-step synthesis compared to the polymer synthesized by one-stepprocedure. The tensile properties were similar in both the cases. Theprocessing was easier, compared to the same TPU synthesized by theone-step procedure.

TABLE 9 M_(n) and tensile property data of PIB-TPU-4321 synthesizedunder different conditions Elongation at Procedure M_(n) (GPC) PDI (GPC)UTS (MPa) break (%) One-step 110000 2.3 7 200 Two-step 119000 1.6 7 150

Example 3 Synthesis of Polyisobutylene/Polyether-Based ThermoplasticUrethane (PIB-PTMO-TPU)

TPUs having mixtures of PIB and PTMO in different proportions as softsegment were synthesized using the two-step procedure according to thesynthetic procedure exemplified in FIG. 2. BDO and MDI constituted thehard segment. The soft segment to hard segment ratio of 80:20 wt % wasmaintained in all the cases.

For example, PIB-PTMO-82-6 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 5.2 g, 2.36 mmol) and PTMO(M_(n)=1000, 1.3 g, 1.3 mmol) were azeotropically distilled from drytoluene (10 mL). The mixture was kept at 45° C. for 3 hours undervacuum. 25 mL of dry toluene was added to this misture, followed bySn(Oct)₂ (28.3 mg, 0.07 mmol) in toluene. The mixture was heated at 80°C. under a slow stream of dry nitrogen gas. MDI (1.76 g, 7.02 mmol) wasadded to this mixture and the mixture was stirred vigorously for 30 min.BDO (302 mg, 3.36 mmol) was added to the resulting reaction mixture andthe mixture was stirred for 4 hours at 100° C. The mixture was cooled toroom temperature, poured in a Teflon® mold and the solvent wasevaporated at room temperature in air for 48 hours. Finally the polymerwas dried under vacuum at 50° C. for 12 hours.

The sample codes and weight percent values of PIB and PTMO is shown inTable 10.

TABLE 10 Weight Percent Values of PIB and PTMO in PIB-PTMO TPU (Shorehardness 60A) HO-PIB-OH¹ HO-PTMO-OH² Code (wt %)³ (wt %)³ PIB-PTMO-91-690 10 PIB-PTMO-82-6 80 20 PIB-PTMO-73-6 70 30 PIB-PTMO-64-6 60 40PIB-PTMO-55-6 50 50 PIB-PTMO-28-6 20 80 PTMO-60A 0 100 ¹HO-PIB-OH, M_(n)= 2200, ²HO-PTMO-OH, M_(n) = 1000, ³soft:hard = 79:21 wt %

GPC-RI traces of the TPUs showed monomodal distribution of molecularweight with the values of molecular weight in the range of 55000-140000and PDI of approximately 1.4-2.7. The molecular weight data of the TPUssynthesized according to the method described above are described inTable 11:

TABLE 11 Molecular weight data of PIB-PTMO TPU (Shore hardness ≈ 60A)Code M_(n) (GPC) PDI PIB-PTMO-91-6 94000 2.1 PIB-PTMO-82-6 129000 2.2PIB-PTMO-73-6 137000 2.7 PIB-PTMO-64-6 95000 2.2 PIB-PTMO-55-6 85000 1.4PIB-PTMO-28-6 55000 1.6 PTMO-60A 33000 1.3

The ultimate tensile strength (UTS) of the PIB-PTMO TPUs wasapproximately 4-20 MPa with elongation at break in the range of400-740%. The Young's moduli of the polymers were obtained in the rangeof 2-9 MPa. The Shore hardness and tensile property data of the TPUs arelisted in Table 12 below:

TABLE 12 Shore hardness and tensile property data of PIB-PTMO TPUYoung's Tensile PTMO Modulus Strength Elongation Polymer (wt %) Shore A(MPa) (MPa) (%) PIB-PTMO-91-6 10 71 8.5 20 400 PIB-PTMO-82-6 20 60 5.218 680 PIB-PTMO-73-6 30 61 4.5 18 740 PIB-PTMO-64-6 40 59 4.7 22 740PIB-PTMO-55-6 50 62 7.5 22 730 PIB-PTMO-28-6 80 61 2 4 400 PTMO-60A 10060 5 10 500

With addition of a small amount of polytetramethyleneoxide diol (PTMO),the mechanical properties of the polymers increased dramatically.However, the properties remained similar with further increase in PTMOcomposition. TPU with 100% PTMO (PTMO-60A) also exhibited similartensile property.

PIB-PTMO TPUs with higher hard segment to soft segment ratio weresynthesized using the two-step procedure described above. The softsegment to hard segment ratio (SS:HS) of 65:35 percent by weight wasmaintained in all the cases, while the PIB to PTMO ratio (in percent byweight of the soft segment) was varied. Results are presented in Table13.

TABLE 13 Percent Weight of PIB and PTMO in PIB-PTMO TPU (Shore hardness80A) HO-PIB-OH¹ HO-PTMO-OH² Code (wt %)³ (wt %)³ PIB-PTMO-91-8 90 10PIB-PTMO-82-8 80 20 PIB-PTMO-73-8 70 30 PIB-PTMO-64-8 60 40PIB-PTMO-28-8 20 80 PTMO-80A 0 100 ¹HO-PIB-OH, M_(n) = 2200,²HO-PTMO-OH, M_(n) = 1000, ³SS:HS = 65:35 wt %

Exemplary Synthesis of a PIB-PTMO-TPU

PIB-PTMO-82-8 was synthesized as follows. HO-Allyl-PIB-Allyl-OH(M_(n)=2200, 5.2 g, 2.36 mmol) and PTMO (M_(n)=1000, 1.3 g, 1.3 mmol)were azeotropically distilled from dry toluene (10 mL). The mixture waskept at 45° C. for 3 hours under vacuum. 25 mL of dry toluene was addedto this mixture, followed by Sn(Oct)₂ (42 mg, 0.104 mmol) in toluene.The mixture was heated at 80° C. under a slow stream of dry nitrogengas. MDI (2.6 g, 10.38 mmol) was added to the reaction mixture, and themixture was stirred vigorously for 30 min. BDO (605 mg, 6.72 mmol) wasadded to the reaction mixture, and the mixture was stirred for 4 hoursat 100° C. The mixture was cooled to room temperature, poured in aTeflon® mold and the solvent was evaporated at room temperature in airfor 48 hours. Finally the polymer was dried under vacuum at 50° C. for12 hours.

Molecular weight data of PIB-PTMO TPUs with Shore hardness of 80 A isshown in Table 14. The molecular weight of the polymers is in the rangeof 42000-138000, with PDI of 1.9-3.8.

TABLE 14 Molecular weight data of PIB-PTMO TPU (Shore hardness 80A) CodeM_(n) (GPC) PDI PIB-PTMO-91-8 84000 1.9 PIB-PTMO-82-8 119000 2.8PIB-PTMO-73-8 138000 3.5 PIB-PTMO-64-8 130000 3.7 PIB-PTMO-28-8 400003.8 PTMO-80A 42000 2.4

The ultimate tensile strength (UTS) of the PIB-PTMO TPUs (Shore hardness80 A) were in the range of 18-25 MPa with elongation at break in therange of 150-550%. The Young's modulus of the polymers were highercompared to PIB-PTMO TPUs with lower Shore hardness (60 A) and variedbetween 11-32 MPa. Increase in PTMO concentration linearly increased theUTS as well as the elongation at break of the TPUs. The PIB-PTMO TPUcomprising PTMO-80A exhibited highest UTS and elongation at break. TheShore hardness and tensile property data of the TPUs are listed in Table15 below.

TABLE 15 Shore hardness and tensile property data of PIB-PTMO TPU (Shorehardness 80A) Young's Tensile Tear Modulus Strength Elongation StrengthPolymer Shore A (MPa) (MPa) (%) (pli) PIB-PTMO-91-8 83 32 18 150 310PIB-PTMO-82-8 82 32 23 400 380 PIB-PTMO-73-8 81 23 27 370 409PIB-PTMO-64-8 81 11 25 550 440 PIB-PTMO-28-8 81 5 8 550 270

Exemplary Synthesis of the PIB-PTMO TPU Performed at 120° C.

PIB-PTMO TPUs having not less than 80 percent by weight of the softsegment of the PTMO component were synthesized according to thesynthetic scheme exemplified in FIG. 2. The soft segment to hard segmentratio (SS:HS) was varied to achieve Shore hardness values of 60 A to 80A.

For example, PIB-PTMO-28-8 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 1.12 g, 0.51 mmol) and PTMO(M_(n)=1000, 4.48 g, 4.48 mmol) were azeotropically distilled from drytoluene (10 mL). The mixture was kept at 45° C. for 3 hours undervacuum. 25 mL of dry toluene was added to the reaction mixture, followedby Sn(Oct)₂ (44.6 mg, 0.11 mmol) in toluene. The mixture was heated at80° C. under a slow stream of dry nitrogen gas. MDI (2. 67 g, 10.7 mmol)was added to the reaction mixture, and the mixture was stirredvigorously for 30 min. BDO (520 mg, 5.7 mmol) was added to the reactionmixture, and the temperature was raised to 120° C. After 15 minutes, thetemperature was decreased to 100° C. and the mixture was kept undernitrogen for 4 hours. The mixture was cooled to room temperature, pouredin a Teflon® mold and the solvent was evaporated at room temperature inair for 48 hours. Finally the polymer was dried under vacuum at 50° C.for 12 hours.

The GPC data of the TPUs having PTMO in excess of 80% by weight of thesoft segment is given in Table 16 below. The molecular weight values ofthese TPUs increased compared to the polymers that were synthesized fromthe same starting materials, but at a temperature of 100° C. (Table 11and 14).

TABLE 16 Molecular Weight Data of PIB-PTMO TPU, Soft Segment Includingnot Less than 80% by Weight of PTMO (Reaction Temperature = 120° C.)Code M_(n) (GPC) PDI PIB-PTMO-28-6 105000 2.3 PTMO-60A 113000 2.0PIB-PTMO-28-8 87000 1.8 PTMO-80A 102000 1.7

The UTS, ultimate elongation at break and Young's modulus data of theTPUs of Table 16 are listed in Table 17 below. The UTS of PTMO-60A(compare to Table 12) increased from 10 MPa to 20 MPa when the syntheticprocedure was modified by increasing the reaction temperature to 120° C.A 200% enhancement in ultimate elongation at break was also observed.Other TPUs also exhibited improved tensile properties, as shown in Table17. The tensile data of the PIB-PTMO-28-6 (see Table 12) andPIB-PTMO-28-8 (see Table 15) synthesized at 100° C. are describedpreviously.

TABLE 17 The Tensile Property of PIB-PTMO TPU, Soft Segment Includingnot Less than 80% by Weight of PTMO (Reaction Temperature = 120° C.)Elongation Young's UTS at break Modulus Code Shore A (MPa) (%) (MPa)PIB-PTMO-28-6 60 22 950 7 PTMO-60A 60 20 700 5 PIB-PTMO-28-8 81 17 740 9PTMO-80A 80 35 800 7Synthesis of PIB-PTMO-TPU (Shore Hardness about 95 A)

PIB-PTMO TPUs with designed Shore hardness of about 95 A weresynthesized using the two-step procedure described above. The softsegment to hard segment ratio (SS:HS) of 60:40 w:w was maintained in allthe cases, while the PIB to PTMO weight ratio was varied as shown inTable 18.

TABLE 18 Percent Weight of PIB and PTMO in PIB-PTMO TPU (Shore hardness95A) HO-PIB-OH¹ HO-PTMO-OH² Code (wt %)³ (wt %)³ PIB-PTMO-91-9 90 10PIB-PTMO-82-9 80 20 PIB-PTMO-73-9 70 30 PIB-PTMO-64-9 60 40PIB-PTMO-55-9 50 50 ¹HO-PIB-OH, M_(n) = 2200, ²HO-PTMO-OH, M_(n) = 1000,³SS:HS = 60:40 wt %

For example, PIB-PTMO-73-9 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 3.92 g, 1.78 mmol) and PTMO(M_(n)=1000, 1.68 g, 1.68 mmol) were azeotropically distilled from drytoluene (10 mL). The mixture was kept at 45° C. for 3 hours undervacuum. 25 mL of dry toluene was added to the reaction mixture, followedby Sn(Oct)₂ (49 mg, 0.121 mmol) in toluene. The mixture was heated at80° C. under a slow stream of dry nitrogen gas. MDI (3.03 g, 12.12 mmol)was added to the reaction mixture, and the mixture was stirredvigorously for 30 min. BDO (780 mg, 8.66 mmol) was added to the reactionmixture, and the mixture was stirred for 4 hours at 100° C. The mixturewas cooled to room temperature, poured in a Teflon® mold and the solventwas evaporated at room temperature in air for 48 hours. Finally, thepolymer was dried under vacuum at 50° C. for 12 hours.

The molecular weight data of PIB-PTMO TPUs with Shore 95 A hardness areshown in Table 19. The molecular weight of the polymers was in the rangeof 79000-111500, with PDI of 1.6-3.4.

TABLE 19 Molecular weight data of PIB-PTMO TPU (Shore hardness 95A) CodeMn (GPC) PDI (GPC) PIB-PTMO-91-9* — — PIB-PTMO-82-9 87000 3.4PIB-PTMO-73-9 79000 1.6 PIB-PTMO-64-9 105000 2.5 PIB-PTMO-55-9 1115002.8 *The TPU is sparingly soluble in THF/TBAB mixture

The UTS, Shore hardness, tear strength and Young's modulus data forPIB-PTMO-TPU (Shore hardness of about 95 A) are presented in Table 20.The UTS and Young's modulus of the polymers were observed in the rangeof 14-42 MPa and 144-17 MPa respectively. The elongation at break wasobserved in the range of 30-510%. The UTS and Young's modulus ofPIB-PTMO-73-9 was higher compared to the TPUs having same PIB/PTMO ratioof 70/30 by weight, such as PIB-PTMO-6 and PIB-PTMO-8 TPUs with Shorehardness 60 A (PIB-PTMO-73-6) and 80 A (PIB-PTMO-73-8).

TABLE 20 Tensile properties of PIB-PTMO-TPU (Shore hardness ≈ 95A)Young's UTS Modulus Elongation at Code Shore A (MPa) (MPa) break (%)PIB-PTMO-91-9 95 14 144 30 PIB-PTMO-82-9 98 29 50 310 PIB-PTMO-73-9 9940 45 350 PIB-PTMO-64-9 98 39 27 430 PIB-PTMO-55-9 96 42 17 510

Example 4 Synthesis of Polyisobutylene/Poly(Alkylenecarbonate)-BasedThermoplastic Urethane (PIB-PHMC-TPU)

TPU, having a mixture of PIB and poly(hexamethylene carbonate) (PHMC) inthe ratio of 70:30 percent by weight of the soft segment was synthesizedusing the procedure similar to the one illustrated in FIG. 2. The hardsegment comprised BDO and MDI. The ratio of hard segment to softsegment, HS:SS, was 21:79 percent by weight.

A synthetic procedure for PIB-PHMC-73-6 is given below. PIB-PHMC-73-6was synthesized as follows. HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 4.5 g,2.04 mmol) and PHMC (M_(n)=860, 1.93 g, 2.27 mmol) were azeotropicallydistilled from dry toluene (10 mL). The reaction mixture was kept at 45°C. for 3 hours under vacuum. 25 mL of dry toluene was added to thereaction mixture, followed by Sn(Oct)₂ (26.3 mg, 0.065 mmol) in toluene.The reaction mixture was heated at 80° C. under a slow stream of drynitrogen gas. MDI (1.63 g, 6.51 mmol) was added to the reaction mixtureand the mixture was stirred vigorously for 30 minutes. BDO (200 mg, 2.2mmol) was added to the reaction mixture and the mixture was stirred for4 hours at 100° C. The reaction mixture was cooled to room temperature,poured in a Teflon® mold, and the solvent was evaporated at roomtemperature in air for 48 hours. Finally, the polymer was dried undervacuum at 50° C. for 12 hours.

The ultimate tensile strength (UTS) of the PIB-PHMC-73-6 was 10 MPa withelongation at break of about 300%. The Young's modulus of the polymerwas 10 MPa with Shore (A) hardness about 61 A.

Example 5 Preparation of an Elastomeric Polymer ComprisingPolyisobutylene-Diamine (H₂N-Allyl-PIB-Allyl-NH₂)

The synthesis of H₂N-Allyl-PIB-Allyl-NH₂ was carried out by heating theTHF:DMF (70:30, v:v) solution of chloroallyl telechelic PIB withphthalimide potassium under reflux conditions for 18 hours followed byhydrolysis in presence of NH₂NH₂.H₂O.

For example, Phthalimide-Allyl-PIB-Allyl-Phthalimide was synthesized asfollows. Cl-Allyl-PIB-Allyl-Cl (M_(n)=2100, 10 g, 0.0048 mol) wasdissolved in dry THF (300 mL) and dry DMF (100 mL) followed by theaddition of phthalimide potassium (50 g, 0.27 mol) and the mixture wasrefluxed under dry nitrogen atmosphere for 18 h. The reaction mixturewas cooled to room temperature, filtered and THF was evaporated.Methanol was added to the sticky mass left over and the precipitate wasseparated and dissolved in hexanes. The solution was reprecipitated inmethanol. The product obtained was further purified by dissolution andreprecipitation using hexanes and methanol.

A typical synthetic procedure for H₂N-Allyl-PIB-Allyl-NH₂ is as follows.Phthalimide-Allyl-PIB-Allyl-Phthalimide (9 g, 0.0042 mol) was dissolvedin THF (200 mL) and hydrazine hydrate (15 g) was added. The mixture wasrefluxed for 24 h. The reaction was stopped and cooled to roomtemperature. A solution of KOH (10 g, in 25 mL of water) was added andstirred for 30 min. THF was evaporated under reduced pressure andmethanol was added. The precipitate obtained was purified by dissolvingin hexanes and reprecipitating in methanol. Yield: 98%, NMR: M_(n)=2100.

Example 6 Synthesis of Polyisobutylene/Poly(Tetramethylene Oxide)-BasedThermoplastic Urethaneurea (PIB-PTMO-TPUU)

A series of PIB based polyurethaneurea with designed Shore 80 A hardnesswas synthesized by chain extension of H₂N-Allyl-PIB-Allyl-NH₂ andHO-PTMO-OH with BDO and MDI as exemplified in FIG. 3. The ratio ofPIB:PTMO was varied and the SS:HS w:w ratio was maintained at 65:35 asshown in Table 21. The synthetic route is is schematically depicted inFIG. 5.

TABLE 21 Percent Weight of PIB and PTMO in PIB-PTMO TPUU (Shore hardness80A) H₂N-PIB-NH₂ ¹ HO-PTMO-OH² PTMO Code (wt % in SS) (wt % in SS) (wt %in TPUU) PIB-TPUU-82-8 80 20 13 PIB-TPUU-73-8 70 30 19 PIB-TPUU-64-8 6040 26 PIB-TPUU-19-8 10 90 59 ¹H₂N-PIB-NH₂ (M_(n)) = 2100, ²HO-PTMO-OH(M_(n)) = 1000

Exemplary Synthesis of a PIB-PTMO-TPUU

PIB-TPUU-82-8 was synthesized as follows. H₂N-Allyl-PIB-Allyl-NH₂(M_(n)=2100, 5.2 g, 2.36 mmol) and PTMO (M_(n)=1000, 1.3 g, 1.3 mmol)were azeotropically distilled from dry toluene (10 mL). The mixture waskept at 45° C. for 3 hours under vacuum. 25 mL of dry toluene was addedto this mixture, followed by Sn(Oct)₂ (42 mg, 0.104 mmol) in toluene.The mixture was heated at 80° C. under a slow stream of dry nitrogengas. MDI (2.6 g, 10.38 mmol) was added to the reaction mixture, and themixture was stirred vigorously for 30 min. BDO (605 mg, 6.72 mmol) wasadded to the reaction mixture and the mixture was stirred for 4 hours at100° C. The mixture was cooled to room temperature, poured in a Teflon®mold and the solvent was evaporated at room temperature in air for 48hours. Finally the polymer was dried under vacuum at 50° C. for 12hours.

Molecular weight data of PIB-PTMO TPUUs with Shore 80 A hardness areshown in Table 22. The molecular weight of the polymers is in the rangeof 98700-119000, with PDI=1.6-2.8.

TABLE 22 Molecular weight data of PIB-PTMO TPUU (Shore hardness 80A)Code M_(n) (GPC) PDI (GPC) PIB-TPUU-82-8 104000 1.8 PIB-TPUU-73-8 987002.5 PIB-TPUU-64-8 106500 2.8 PIB-TPUU-19-8 119000 1.6

The UTS, Shore hardness, tear strength and Young's modulus data forPIB-PTMO-TPUU are presented in Table 23. The UTS of the polymers wasobserved in the range of 23-32 MPa and the Young's modulus variedbetween 5 to 50 MPa. The elongation at break was observed in the rangeof 250-675%.

TABLE 23 Tensile properties of PIB-PTMO-TPUU (Shore hardness ≈ 80A)Young's UTS Modulus Elongation at Code Shore A (MPa) (MPa) break (%)PIB-TPUU-82-8 86 23 50 250 PIB-TPUU-73-8 85 26 30 310 PIB-TPUU-64-8 8932 21 420 PIB-TPUU-19-8 86 29 5 675

Example 4 Mechanical Measurements of Selected Sample TPUs

Ultimate tensile strength (UTS) and elongation at break were measured asdescribed above for eight samples:

A, PIB-TPU-2221 (shown in Table 7),

B, PIB-PTMO-91-6 (shown in Table 12),

C, PIB-PTMO-82-6 (shown in Table 12),

D, PIB-PTMO-73-6 (shown in Table 12),

E, PIB-PTMO-64-6 (shown in Table 12),

F, PIB-PTMO-55-6 (shown in Table 12),

G, PIB-PTMO-28-6 (shown in Table 12), and

H, PTMO-60A (shown in Table 17).

These samples were synthesized according to the procedure described inExample 3, above. The samples differed in the content of PTMO, apolyether diol.

The results are presented in FIG. 3 and FIG. 4. As can be seen, additionof PTMO improves the mechanical properties of a PIB-based TPU, comparedwith Sample A. Furthermore, comparison with Sample H, which does notcontain any PIB shows that the TPUs based on a combination of the PIBmacrodiols and polyether macrodiols possess mechanical properties thatare superior to the TPUs based on PIB macrodiols or polyether macrodiolalone.

Example 7 Synthesis of Polyisobutylene/Polyether-Based ThermoplasticUrethane (PIB-PTMO-TPU, 50 A Shore Hardness)

TPU having mixture of PIB and PTMO in 80:20 weight proportion as softsegment was synthesized using the two-step procedure according to thesynthetic procedure exemplified in FIG. 2. BDO and MDI constituted thehard segment. The soft segment to hard segment ratio of 82:18 wt % wasmaintained.

For example, PIB-PTMO-82-5 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2250, 5.0 g, 2.2 mmol) and PTMO(M_(n)=1000, 1.25 g, 1.25 mmol) were dried by azeotropic distillationfrom dry toluene (10 mL) solution. The mixture was kept at 45° C. for 3hours under vacuum. 25 mL of dry toluene was added to this mixture,followed by Sn(Oct)₂ (20.3 mg, 0.05 mmol) in toluene. The mixture washeated at 80° C. under a slow stream of dry nitrogen gas. MDI (1.32 g,5.3 mmol) was added to this mixture and the mixture was stirredvigorously for 30 min. BDO (170 mg, 1.87 mmol) was added to theresulting reaction mixture and the mixture was stirred for 4 hours at100° C. The mixture was cooled to room temperature, poured in a Teflon®mold and the solvent was evaporated at room temperature in air for 48hours. Finally the polymer was dried under vacuum at 50° C. for 12hours.

The TPU exhibited the following characteristics: M_(n)=75000, PDI=1.7,UTS=14 MPa and elongation at break=800%, Young's modulus=3 MPa, flexuralmodulus=11 MPa, tear strength=292 pli.

Example 8 Synthesis of Polyisobutylene/Polyether-Based ThermoplasticUrethane (PIB-PTMO-TPU, 55 A Shore Hardness)

TPU having mixture of PIB and PTMO in 80:20 weight proportion as softsegment was synthesized using the two-step procedure according to thesynthetic procedure exemplified in FIG. 2. BDO and MDI constituted thehard segment. The soft segment to hard segment ratio of 81:19 wt % wasmaintained.

For example, PIB-PTMO-82-5.5 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2250, 5.4 g, 2.4 mmol) and PTMO(M_(n)=1000, 1.35 g, 1.35 mmol) were dried by azeotropic distillationfrom dry toluene (10 mL) solution. The mixture was kept at 45° C. for 3hours under vacuum. 25 mL of dry toluene was added to this mixture,followed by Sn(Oct)₂ (25.9 mg, 0.06 mmol) in toluene. The mixture washeated at 80° C. under a slow stream of dry nitrogen gas. MDI (1.55 g,6.21 mmol) was added to this mixture and the mixture was stirredvigorously for 30 min. BDO (223 mg, 2.46 mmol) was added to theresulting reaction mixture and the mixture was stirred for 4 hours at100° C. The mixture was cooled to room temperature, poured in a Teflon®mold and the solvent was evaporated at room temperature in air for 48hours. Finally the polymer was dried under vacuum at 50° C. for 12hours.

The TPU exhibited the following characteristics: M_(n)=105000, PDI=2.0,UTS=13 MPa, elongation at break=900%, Young's modulus=3.6 MPa, tearstrength is 295 pli.

Example 9 Synthesis of (Saturated) Polyisobutylene/Polyether-BasedThermoplastic Urethane PIB_(sat)-PTMO-TPU 60 A Shore Hardness

TPU having mixtures of hydroxypropyl telechelic PIB and PTMO indifferent weight proportions as soft segment was synthesized using thetwo-step procedure according to the synthetic procedure exemplified inFIG. 2. BDO and MDI constituted the hard segment. The soft segment tohard segment ratio of 77:23 wt % was maintained.

For example, PIB_(sat)-PTMO-82-6 was synthesized as follows.HO-propyl-PIB-propyl-OH (M_(n)=2000, 5.3 g, 2.65 mmol), obtained byhydroboration oxidation of allyl telechelic PIB (Iván, B.; Kennedy, J.P. J. Polym. Sci., Part A: Polym. Chem. 1990, 28, 89), and PTMO(M_(n)=1000, 1.33 g, 1.33 mmol) were dried by azeotropic distillationfrom dry toluene (10 mL) solution. The mixture was kept at 45° C. for 3hours under vacuum. 25 mL of dry toluene was added to this mixture,followed by Sn(Oct)₂ (29.9 mg, 0.074 mmol) in toluene. The mixture washeated at 80° C. under a slow stream of dry nitrogen gas. MDI (1.84 g,7.36 mmol) was added to this mixture and the mixture was stirredvigorously for 30 min. BDO (308 mg, 3.38 mmol) was added to theresulting reaction mixture and the mixture was stirred for 4 hours at100° C. The mixture was cooled to room temperature, poured in a Teflon®mold and the solvent was evaporated at room temperature in air for 48hours. Finally the polymer was dried under vacuum at 50° C. for 12hours.

The TPU exhibited the following characteristics: M modu_(n)=140000,PDI=2.2, UTS=20 MPa, elongation at break=550%, Young's lus=6 MPa.

Example 10 Synthesis of Polyisobutylene (Saturated)/Polyether-BasedThermoplastic Urethane PIB_(sat)-PTMO-TPU, 80 A Shore Hardness)

TPU having mixtures of hydroxypropyl telechelic PIB and PTMO indifferent weight proportions as soft segment was synthesized using thetwo-step procedure according to the synthetic procedure exemplified inFIG. 2. BDO and MDI constituted the hard segment. The soft segment tohard segment ratio of 66:34 wt % was maintained in all the cases.

PIB_(sat)-PTMO-82-8 was synthesized as follows. HO-propyl-PIB-propyl-OH(M_(n)=2000, 5.2 g, 2.6 mmol) and PTMO (M_(n)=1000, 1.3 g, 1.3 mmol)were dried by azeotropic distillation from dry toluene (10 mL) solution.The mixture was kept at 45° C. for 3 hours under vacuum. 25 mL of drytoluene was added to this mixture, followed by Sn(Oct)₂ (42.5 mg, 0.105mmol) in toluene. The mixture was heated at 80° C. under a slow streamof dry nitrogen gas. MDI (2.64 g, 10.54 mmol) was added to the reactionmixture, and the mixture was stirred vigorously for 30 min. BDO (604 mg,6.64 mmol) was added to the reaction mixture, and the mixture wasstirred for 4 hours at 100° C. The mixture was cooled to roomtemperature, poured in a Teflon® mold and the solvent was evaporated atroom temperature in air for 48 hours. Finally the polymer was driedunder vacuum at 50° C. for 12 hours.

The TPU exhibited the following characteristics: M_(n)=85000, PDI=2.2,UTS=27 MPa, elongation at break=475%, Young's modulus=15 MPa.

Example 11 Synthesis of Polyisobutylene/Polyether-Based ThermoplasticUrethane (PIB-Polyhexamethylene Oxide(PHMO)-TPU, 80 A Shore Hardness)

TPU having mixtures of PIB and PHMO in different weight proportions assoft segment was synthesized using the two-step procedure according tothe synthetic procedure exemplified in FIG. 2. BDO and MDI constitutedthe hard segment. The soft segment to hard segment ratio of 67:33 wt %was maintained.

For example, PIB-PHMO-82-8 was synthesized as follows.HO-Allyl-PIB-Allyl-OH (M_(n)=2200, 4.6 g, 2.1 mmol) and PHMO (M_(n)=920,1.15 g, 1.25 mmol) were dried by azeotropic distillation from drytoluene (10 mL) solution. The mixture was kept at 45° C. for 3 hoursunder vacuum. 25 mL of dry toluene was added to this mixture, followedby Sn(Oct)₂ (37.26 mg, 0.092 mmol) in toluene. The mixture was heated at80° C. under a slow stream of dry nitrogen gas. MDI (2.3 g, 9.22 mmol)was added to this mixture and the mixture was stirred vigorously for 30min. BDO (534 mg, 5.87 mmol) was added to the resulting reaction mixtureand the mixture was stirred for 4 hours at 100° C. The mixture wascooled to room temperature, poured in a Teflon® mold and the solvent wasevaporated at room temperature in air for 48 hours. Finally the polymerwas dried under vacuum at 50° C. for 12 hours.

The TPU exhibited the following characteristics: M_(n)=73000, PDI=3.4,UTS=18 MPa, elongation at break=280%, Young's modulus=27 MPa.

Example 12 Synthesis of Polyisobutylene (Saturated)/Polyether-BasedThermoplastic Urethane PIB_(sat)-PHMO-TPU 60 A Shore Hardness

TPU having mixtures of hydroxypropyl telechelic PIB and PHMO indifferent weight proportions as soft segment was synthesized using thetwo-step procedure according to the synthetic procedure exemplified inFIG. 2. BDO and MDI constituted the hard segment. The soft segment tohard segment ratio of 76:24 wt % was maintained in all the cases.

For example, PIB_(sat)-PHMO-82-6 was synthesized as follows.HO-propyl-PIB-propyl-OH (M_(n)=2000, 4.6 g, 2.3 mmol) and PHMO(M_(n)=920, 1.15 g, 1.25 mmol) were dried by azeotropic distillationfrom dry toluene (10 mL) solution. The mixture was kept at 45° C. for 3hours under vacuum. 25 mL of dry toluene was added to this mixture,followed by Sn(Oct)₂ (26.3 mg, 0.065 mmol) in toluene. The mixture washeated at 80° C. under a slow stream of dry nitrogen gas. MDI (1.62 g,6.48 mmol) was added to this mixture and the mixture was stirredvigorously for 30 min. BDO (267 mg, 2.93 mmol) was added to theresulting reaction mixture and the mixture was stirred for 4 hours at100° C. The mixture was cooled to room temperature, poured in a Teflon®mold and the solvent was evaporated at room temperature in air for 48hours. Finally the polymer was dried under vacuum at 50° C. for 12hours.

The TPU exhibited the following characteristics: M_(n)=120000, PDI=3.4,UTS=16 MPa, elongation at break=550%, Young's modulus=6 MPa.

Example 13 Synthesis of Polyisobutylene (Saturated)/Polyether-BasedThermoplastic Urethane (PIB_(sat)-PTMO-TPU, 95 A Shore Hardness) WithoutCatalyst

TPU having mixtures of hydroxypropyl telechelic PIB and PTMO-diol indifferent weight proportions as soft segment was synthesized using thetwo-step procedure according to the synthetic procedure exemplified inFIG. 2. BDO and MDI constituted the hard segment. The ration of softsegment to hard segment of 60:40 wt % was maintained in all the cases.

For example, PIB_(sat)-PTMO-82-9 was synthesized as follows.HO-propyl-PIB-propyl-OH (M_(n)=2000, 2.8 g, 1.4 mmol) and PTMO(M_(n)=1000, 0.8 g, 0.8 mmol) were dried by azeotropic distillation fromdry toluene (10 mL) solution. The mixture was kept at 45° C. for 3 hoursunder vacuum and 25 mL of dry toluene was added to this mixture. Thetemperature of the mixture was raised to 100° C. under a slow stream ofdry nitrogen gas. MDI (1.92 g, 7.7 mmol) was added to this mixture andthe mixture was stirred vigorously for 1 h and 30 min. BDO (500 mg, 5.5mmol) was added to the resulting reaction mixture and the mixture wasstirred for 4 hours at 100° C. The mixture was cooled to roomtemperature, poured in a Teflon mold and the solvent was evaporated atroom temperature in air for 48 hours. Finally the polymer was driedunder vacuum at 50° C. for 12 hours.

The TPU exhibited the following characteristics: M_(n)=88000, PDI=3.7.

Example 14 Long Term In Vitro Biostability of SegmentedPolyisobutylene-Based Thermoplastic Polyurethanes

Long term in vitro biostability of termoplastic polyurethanes (TPUs)containing mixed polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO)soft segment was studied under accelerated conditions in 20% H₂O₂solution containing 0.1M CoCl₂ at 50° C. to predict resistance to metalion oxidative degradation in vivo. The PIB-based TPUs containing PTMOshowed significant oxidative stability as compared to the commercialcontrols such as Pellethane™ 2686-55D and 2686-80A. After 12 weeks invitro (equivalent of approximately 10 years in vivo) the PIB-PTMO TPUswith 10-20% PTMO in the soft segment showed 6-15% weight loss whereasthe Pellethanes™ degraded completely in about 9 weeks. The weight losswas linearly proportional to the PTMO content in the PIB-PTMO TPUs.ATR-FTIR spectroscopy confirmed the degradation of Pellethanes™™ via MIOby the consistent loss of the approximately 1110 cm⁻¹ aliphatic C—O—Cstretching peak height attributed to chain scission, and the appearanceof a new peak approximately 1174 cm⁻¹ attributed crosslinking. No suchabsorption bands were apparent in the spectra of the PIB-based TPUs. ThePIB-based TPUs exhibited 10-30% drop in tensile strength compared to100% for the Pellethanes™ after 12 weeks. The drop in tensile strengthcorrelated approximately with PTMO content in the TPU. Molecular weightresults correlated well with tensile strength, showing a slight decrease10-15% at 12 weeks. The Pellethanes™ showed a dramatic decrease in Mn aswell as an increase in low molecular weight degradation product. SEMshowed severe cracking in the Pellethanes™ after two weeks, whereas thePIB-based TPUs exhibited a continuous surface morphology. The weightloss, tensile, and SEM data correlate well with each other and indicateexcellent biostability of these materials.

Materials and Methods Polyurethanes

Control samples consisted of Pellethane™ 2363-55D and Pellethane™2363-80A. Polyurethanes of varying hardness and PIB:PTMO compositionswere synthesized as reported previously and are listed in Table 24. Thetwo-stage process is described for a representative TPU (60A 82) asfollows: HO-Allyl-PIB-Allyl-OH (Mn=2200 g/mol, 5.2 g, 2.36 mmol) andPTMO (Mn=1000 g/mol, 1.3 g, 1.3 mmol) were dried by azeotropicdistillation using dry toluene (10 mL). The mixture was kept at 45° C.for 3 hours under vacuum. To it 25 mL of dry toluene was added followedby Sn(Oct)₂ (28.3 mg, 0.07 mmol) in toluene. The mixture was heated at80° C. under a slow stream of dry nitrogen gas. To it MDI (1.76 g, 7.02mmol) was added and the mixture was stirred vigorously for 30 min. To itBDO (302 mg, 3.36 mmol) was added and the mixture was stirred at 100° C.for 4 hours. The mixture was cooled to room temperature, poured into aTeflon® mold and the solvent was evaporated at room temperature in airfor 48 hours. Finally, the polymer was dried under vacuum at 50° C. for12 hours. A PIB TPU without PTMO was prepared similarly. The saturatedPIB-PTMO polyurethane was synthesized using HO-propyl-PIB-propyl-OH,prepared using a method developed by Kennedy (Ivan, B.; Kennedy, J. P.J. Polym. Sci., Part A: Polym. Chem. 1990, 28, 89). The polyurethaneswere characterized prior to accelerated degradation using 1H NMR andGPC. The harder compositions (80A 91, 100A) did not dissolve in the GPCeluent.

TABLE 24 PIB and PTMO wt % HO- PTMO HO-PIB-OH^(a) PTMO-OH^(b) SS:HS wt %Shore A Code (wt % in SS) (wt % in SS) (wt:wt) in TPU hardness P55D 0100 60:40 60 100 P80A 0 100 65:35 65 80 60A 82 80 20 79:21 16 60 60A 9190 10 79:21 8 60 80A 73 70 30 65:35 19.5 80 80A 82 80 20 65:35 13 80 80A91 90 10 65:35 6.5 80 100A 82 80 20 60:40 12 100 PIB 60A 100 0 79:21 060 SAT 60A 90 10 79:21 8 60 91 ^(a)HO-PIB-OH, Mn = 2200 g/mol.^(b)HO-PTMO-OH, Mn = 1000 g/mol

The polyurethanes were compression molded using a Carver LaboratoryPress model C at a load of 16,000 lbs. at 160° C. They were molded intothin films ranging in thickness from 0.2 mm-0.5 mm and cut intorectangular strips with approximate dimensions of 3 mm in width and 30mm in length.

In Vitro Accelerated Degradation

The samples were placed in vials and soaked in a 20% H₂O₂ in aqueous 0.1M CoCl₂ solution and stored at 50° C. The solutions were changed everyother day to ensure a steady concentration of radicals. At time pointsafter 1, 2, 4, 6, and 12 weeks, dedicated samples were removed from theoxidative environment, washed 7 times in aqueous 1% Triton X-100surfactant solution, 5 times in ethanol, and 5 times in distilled waterand dried under vacuum at 80° C. until constant weight.

Characterization

Dry samples were characterized by weight loss, ATR-FTIR, ultimatetensile strength, elongation at break, SEM, and GPC. Each data pointconsisted of three identical samples. Of the quantitative data, thereported value is an average of the three samples.

ATR-FTIR

ATR-FTIR was performed on a Thermo Electron Corporation Nicolet 4700FT-IR with a Thermo Electron Corporation Smart Orbit attachment for ATRwith a diamond crystal. Thirty-two scans were averaged to obtain onerepresentative spectrum for each sample. The respective dry clean TPUstrip was placed on the crystal, firmly secured using the footattachment, and scanned for analysis. The region of interest was betweenapproximately 1700 cm⁻¹ and 1100 cm⁻¹, which includes HS degradationproduct (approximately 1650 cm⁻¹), SS degradation moiety (approximately1110 cm⁻¹) and product (approximately 1170 cm⁻¹) and the normalizedreference peak (approximately 1410 cm⁻¹).

Weight Loss

Weights were measured of dry polyurethane films before and afteroxidative treatment on a Sartorius MC1 Analytic AC 210S balance.

Mechanical Testing

Tensile testing was performed at room temperature and atmosphericconditions with a 50 lb. load cell on an Instron Model Tensile Tester4400R at 50 mm/min extension rate until failure. Ultimate tensilestrength and elongation at break were recorded.

GPC Analysis

Molecular weights and molecular weight distributions were measured witha Waters HPLC system equipped with a model 510 HPLC pump, model 410differential refractometer, model 441 absorbance detector, onlinemultiangle laser light scattering (MALLS) detector (MiniDawn, WyattTechnology Inc.), Model 712 sample processor, and five Ultrastyragel GPCcolumns connected in the following series: 500, 10³, 10⁴, 10⁵, and 100Å. THF:TBAB (98:2, wt:wt) was used as a carrier solvent with a flow rateof 1 mL/min.

Scanning Electron Microscopy

Portions of the dry treated films were isolated for SEM analysis.Surface morphology was observed on gold sputter coated samples using aDenton Vacuum Desk IV Cold Cathode Sputter Coater. The samples weresputter coated for 1.5 min at 25% power, corresponding to a thickness ofapproximately 15 Å of gold. The coated samples were observed using aJEOL model JSM 7401F field emission scanning electron microscope.Several representative pictures were taken at 30× and 300×magnification.

3. Results and discussion

ATR-FTIR

ATR-FTIR analysis was performed to confirm the presence and progressionof the MIO mechanism as put forth by Schubert and coworkers. Accordingto their suggested mechanism, a hydroxyl radical may abstract anα-hydrogen from the polyether segment. The resulting radical may combinewith another chain radical to form a crosslink junction or react withanother hydroxyl radical to form a hemiacetal. The hemiacetal oxidizesto ester which is subsequently acid hydrolyzed resulting in chainscission. Therefore progression of degradation can be observed byfollowing the disappearance of the SS ether peak and/or the appearanceof the crosslinking peak. All spectra were normalized to the peak at1410 cm⁻¹, which corresponds to the aromatic C-C stretch of the hardsegment.

The PIB-PTMO polyurethanes all show very small changes in the FTIRspectrum. A representative spectrum, that of 60A 82, is shown in FIG. 6.

As can be seen, There is no appreciable change in the aliphatic etherC—O—C absorbance at 1110 cm⁻¹ and C—O—C branching absorbance atapproximately 1174 cm⁻¹ is absent. However, an increase in the aliphaticabsorbances with time is observed (aliphatic CH2 bending at 1470 cm⁻¹,PIB dimethyl wag at 1388 cm⁻¹, and aliphatic α-CH2 wag at 1365 cm⁻¹).This behavior can be rationalized by migration of PIB segments to thesurface during vacuum drying at 80° C. In these PIB-PTMO TPUscross-linking may be absent since there is not a significant presence ormobility of PTMO to allow two polymer radicals to combine before theyare otherwise cleaved. Similar results are observed in the otherPIB-PTMO TPU spectra. The Sat 60A 91 batch was included in this study todetermine if the unsaturated allyl moiety in the PIB diol was vulnerableto oxidation. The FTIR spectrum of the TPU using the saturated diolappears identical to that of the TPU containing unsaturated diol.Additionally the PIB 60A TPU was included to confirm that there is onlypolyether SS degradation, and not HS degradation in these TPUs. Thishypothesis was confirmed as the spectrum shows no change at all. Thereis no change in the PIB absorbance at 1388 cm⁻¹ or ether absorbance at1111 cm⁻¹ since there is no polyether to be degraded. There is also noevidence of HS degradation. In Table 25 are listed the IR absorbanceswhere trends of change were observed.

TABLE 25 Assigned ATR-FTIR Spectral Peak Changes Wave number PIB- (cm−1)Proposed peak assignment P80A P55D PTMO 1637 NH2 aromatic amine X 1476Aliphatic CH2 bend X 1388 PIB CH3 wag X 1365 Aliphatic α-CH2 wag X X X1173 C—O—C branching X X 1110 Aliphatic C—O—C X X

The Pellethane™ samples showed the expected behavior as is consistentwith previous studies. The spectra of P55D are shown in FIG. 7.

The spectrum shows a significant decrease in aliphatic C—O—C absorptionat 1109 cm⁻¹ after 1 week, then more slowly until 6 weeks. Concurrently,we observe a rapid disappearance of the aliphatic α-CH2 absorbance at1364 cm⁻¹ after just one week. Also the C—O—C branching absorbance at1172 cm⁻¹ is observed immediately at 1 week, then stays constant inmagnitude. As it will be seen later, the Pellethanes™ continued todegrade at a constant, if not accelerated rate after 1 week, and so anexplanation is in order for the IR spectra. ATR-FTIR is a surfacecharacterization technique and degradation is expected to begin at thesurface. Therefore we conclude that the segments vulnerable at thesurface are oxidized almost immediately and deeper oxidation occurs inthe following weeks as observed from the rest of the analyses.

Weight Loss

The weight loss plotted against time is shown in FIG. 8. The PIB-PTMOTPUs all show very low weight loss after 12 weeks ranging from values of6-15% depending on the composition. Among the 60 A batch, the 90/10composition showed lower weight loss of 6% compared to 8% for the 80/20composition. The Sat 60A 91 shows weight loss comparable to theunsaturated 60A 91. Similarly in the 80 A batch, the TPUs with lowerPTMO content showed lower weight loss, from 15, 10 and 6% for 30, 20,and 10% PTMO respectively. More specifically, the weight loss could becorrelated to the PTMO content in the polyurethanes. In FIG. 9 weightloss at 12 weeks vs. PTMO content is plotted.

As can be seen for the PIB-PTMO TPUs there is approximately a linearrelationship between the weight loss and the PTMO content. Thisdiscovery supports the notion that it is the polyether SS which degradesvia MIO and it is these portions which are excised from thepolyurethane. Interestingly, 60A 82 showed a lower weight loss thanexpected for its PTMO content. The TPU which contained only PIB alsoshowed a small weight loss, which fits the plot. Since there is such alarge surface area to volume ratio, we expect to see some small erosionfrom the surface. The Pellethane™ control samples showed noticeableweight loss even after 1 week in vitro, and P80A and P55D completelydegraded after approximately 7 and 9 weeks, respectively. These findingsare consistent with previous findings concerning such polyether basedTPUs.

Mechanical Properties

Tensile strength is plotted as a percentage of the original untreatedsample vs. time in FIG. 10.

A drastic difference in the plots for P55D versus the PIB-PTMO TPUs canbe seen. In the PIB-PTMO TPUs a minimal decrease in tensile strength isobserved for all samples, although the rate of tensile loss varies forthe different samples. The PIB-PTMO TPUs show differing losses which areroughly correlated to the PTMO content. Among the 60 A batch, thetensile losses from the different compositions are comparable. The 12weeks data point for the 60A 91 could not be obtained because of a poorsample set. Nevertheless, the trend observed up to 6 weeks follows veryclosely that of the Sat 60A 91. Minimal decrease in tensile strength wasalso observed in the 60A PIB sample, which showed no degradation asevident from weight loss and FTIR studies. This indicates that 1-2 MPamay be within experimental error with the load cell and instrument used.Among the 80A batch the 80/20 composition shows ˜21% drop in tensilestrength, whereas the 90/10 composition shows only a decrease of ˜13%.The 80A 73 sample (not shown) showed an initial increase in tensilestrength, then subsequently a slower decrease. This is attributed to bedue to crosslinking initially, followed by chain scission consistentwith the increased amount of PTMO in this sample. At this amount of PTMO(19.5% of total TPU), there are sufficient concentration of chainradicals such that crosslinking is able to occur as well as chainscission. Although the % tensile strength at 12 weeks is greater thanthe other PIB-PTMO TPUs, extrapolation of the data would predict thatthe tensile strength 80A 73 would drop more sharply at longer timeintervals.

P55D shows greater resistance to degradation compared to P80A due tomore crystallinity. Thus the 100A 82 composition is expected to havecomparable if not better strength than the 80A 82 composition, yet wesee greater tensile drop. This may suggest that PIB is a betterprotector of the surface than the hard segment. Some of the samplesactually show inhibition periods wherein the tensile strength does notbegin to decrease until 2, 4, or even 6 weeks (esp. 80A 82). Theultimate elongation of the PIB-PTMO TPUs did not change significantlyover the course of the treatment. The Pellethanes™ again showed expectedof MIO behavior. P55D showed gradual tensile loss over time up to 6weeks, and at 12 weeks there was no sample to test. P80A (not shown)showed an initial increase in tensile strength after one week, then agradual decrease.

This is explained by crosslinking of the chains initially, with chainscission occurring afterward as was observed with 80A 73.

GPC Analysis

The TPU samples were dissolved in the carrier solvent of THF:TBAB (98:2,wt:wt). However, some of the harder compositions could not be dissolved.Representative GPC RI traces are shown FIG. 11 for Sat 60A91. The TBABelutes beyond 47 minutes.

The loss in molecular weight is minimal in agreement with the weightloss and tensile data. Mn decreases slightly from 130,000 g/mol to112,000 g/mol after 6 weeks, then negligibly to 110,000 g/mol at 12weeks while the PDI remained unchanged at 1.6. These data are inagreement with the FTIR and tensile data.

In FIG. 12 the refractive index traces of P80A are shown. The numberaverage molecular weight shows a clear trend decreasing from 84,000g/mol before treatment to 18,000 g/mol at 4 weeks and 14,000 g/mol at 6weeks. There is a clearly visible rise in some low molecular weightdegradation product(s) by 4 weeks. Simultaneously there is an increasein the molecular weight distribution. These findings are in agreementwith the ATR-FTIR, weight loss, and tensile results. P55D shows similarbehavior with decreasing Mn and increasing PDI.

SEM

Representative SEM pictures taken at 300× magnification are shown inFIGS. 13-16. Shown in FIG. 13 is P55D which shows the often observedbehavior of “mud cracking” with treatment time. The surface density ofcracks increases with time, and the visual inspection affirms theprevious data as well.

In FIG. 14, FIG. 15 and FIG. 16, scanning electron micrographs of the80A series are shown to depict the effect of PTMO content on the surfacemorphology. The responses of these TPUs to degradation are certainlydifferent than the Pellethanes™, but a trend of increasing surfaceimperfections with increasing PTMO content can be seen. The 80A 73 showssome small holes as well as surface roughening after 12 weeks. 80A 82shows somewhat larger craters after 12 weeks, and 80A 91 showsessentially no change in the surface morphology after 12 weeks. Somesmall holes are often observed in various samples, but these are notexpected to be due to degradation. The same patterns were observed inthe 60A PIB samples, which did not degrade; therefore such holes areexpected to be an artifact of the compression molding process.

The 60A series show analogous morphologies, with the 90/10 compositionshowing a less flawed surface. The 100A 82 composition shows morphologycomparable to 80A91.

Conclusion

After 12 weeks in vitro, which correlates to approximately 10 years invivo, the thermoplastic polyurethanes of the present invention showedminimal degradation and minimal decrease in performance. Usingunsaturated PIB diol rather than saturated PIB diol did not have aneffect on the degradation of the thermoplastic polyurethanes of theinvention. The PIB segment and the hard segment were not observed todegrade. Increasing the amount of polyether diol incorporated in thethermoplastic polyurethanes of the invention increased the degradationrate, suggesting a degradation mechanism identical to that postulatedbefore for PTMO-based thermoplastic polyurethanes. Therefore, a low PTMOcontent was considered to be desirable to ensure biostability.

Equivalents

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

We claim:
 1. A polyurethane or polyurea polymer comprising: a hardsegment in an amount of 10% to 60% by weight of the polymer, the hardsegment including at least one of a urethane, a urea, or a urethaneurea; and a soft segment in an amount of 40% to 90% by weight of thepolymer, the soft segment including: at least one polycarbonatemacrodiol in the amount of 10% to 90% by weight of the soft segment and;at least one of a polyisobutylene macrodiol and a polyisobutylenediamine, the at least one of the polyisobutylene macrodiol and thepolyisobutylene diamine in amount of 10% to 90% by weight of the softsegment; wherein the number average molecular weight of the polymer isgreater or equal to 40 kilodaltons.
 2. The polymer of claim 1, whereinthe at least one of the polyisobutylene macrodiol and thepolyisobutylene diamine is of a formula:

wherein: each X is independently —OH, —NH₂ or —NHR₄; R_(I) is aninitiator residue; R₂ and R₃ and R₄ is each independently a C1-C16alkyl, a C3-C16 cycloalkyl, a C2-C16 alkenyl, a C3-C 16 cycloalkenyl, ora C6-C 18 aryl, wherein, for each occurrence, R₂ or R₃ is,independently, optionally substituted with one or more groups selectedfrom halo, cyano, nitro, dialkylamino, trialkylamino, C1-C16 alkoxy andC1-C16 haloalkyl; and n and m are each, independently, integers from 1to
 500. 3. The polymer of claim 1, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine ishydroxyallyl telechelic polyisobutylene.
 4. The polymer of claim 1,wherein the at least one of the polyisobutylene macrodiol and thepolyisobutylene diamine is hydroxyalkyl telechelic polyisobutylene. 5.The polymer of claim 4, wherein the hydroxyalkyl telechelicpolyisobutylene is hydroxypropyl telechelic polyisobutylene.
 6. Thepolymer of claim 1, wherein the at least one of the polyisobutylenemacrodiol and the polyisobutylene diamine is a polyisobutylene macrodioland the number average molecular weight of the polyisobutylene macrodiolis about 400 Da to about 6000 Da.
 7. The polymer of claim 1, wherein theat least one polycarbonate macrodiol includes at least one poly(alkylenecarbonate).
 8. The polymer of claim 1, wherein the hard segment furtherincludes a diisocyanate residue and a chain extender.
 9. The polymer ofclaim 8, wherein the diisocyanate is 4,4′-methylenephenyl diisocyanateand wherein the chain extender is 1,4-butanediol.
 10. The polymer ofclaim 1, wherein: the polyisobutylene macrodiol of the soft segmentcomprises a hydroxylalkyl telechelic polyisobutylene residue; and thehard segment comprises a 4,4′-methylenediphenyl diisocyanate and1,4-butanediol chain extender.
 11. The polymer of claim 1, wherein theat least one polycarbonate macrodiol is in an amount of 10% to 30% byweight of the soft segment, and the at least one of the polyisobutylenemacrodiol and the polyisobutylene diamine is in an amount of 70% to 90%by weight of the soft segment.
 12. A medical device comprising: apolyurethane or polyurea polymer including: a hard segment in an amountof 10% to 60% by weight of the polymer, the hard segment including atleast one of a urethane, a urea, or a urethane urea; and a soft segmentin an amount of 40% to 90% by weight of the polymer, the soft segmentincluding: at least one polycarbonate macrodiol in the amount of 10% to90% by weight of the soft segment and; at least one of a polyisobutylenemacrodiol and a polyisobutylene diamine, the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine in amount of10% to 90% by weight of the soft segment; wherein the number averagemolecular weight of the polymer is greater than or equal to 40kilodaltons.
 13. The medical device of claim 12, wherein the medicaldevice is selected from the group consisting of a cardiac pacemaker, adefibrillator, a catheter, an implantable prosthesis, a cardiac assistdevice, an artificial organ, a pacemaker lead, a defibrillator lead, ablood pump, a balloon pump, an AV shunt, a biosensor, a membrane forcell encapsulation, a drug delivery device, a wound dressing, anartificial joint, an orthopedic implant or a soft tissue replacement.14. A method for preparing a polyurethane or polyurea polymer, themethod comprising: reacting a diisocyanate with a mixture that includesat least one polyisobutylene macrodiol and/or diamine, and at least onepolycarbonate macrodiol, to form a prepolymer having terminally reactivediisocyanate groups; and reacting the prepolymer with a chain extenderto yield the polymer, wherein the polymer includes: a hard segment in anamount of 10% to 60% by weight of the polymer, the hard segmentincluding at least one of a urethane, a urea, or a urethane urea; and asoft segment in an amount of 40% to 90% by weight of the polymer, thesoft segment including: at least one polycarbonate macrodiol in theamount of 10% to 90% by weight of the soft segment and; at least one ofa polyisobutylene macrodiol and a polyisobutylene diamine, the at leastone of the polyisobutylene macrodiol and the polyisobutylene diamine inamount of 10% to 90% by weight of the soft segment; wherein the numberaverage molecular weight of the polymer is greater than or equal to 40kilodaltons.
 15. The method of claim 14, wherein the at least one of thepolyisobutylene macrodiol and the polyisobutylene diamine is of aformula:

wherein: each X is independently —OH, —NH₂ or —NHR₄; R_(I) is aninitiator residue; R₂ and R₃ and R₄ is each independently a C1-C16alkyl, a C3-C16 cycloalkyl, a C2-C16 alkenyl, a C3-C 16 cycloalkenyl, ora C6-C 18 aryl, wherein, for each occurrence, R₂ or R₃ is,independently, optionally substituted with one or more groups selectedfrom halo, cyano, nitro, dialkylamino, trialkylamino, C1-C16 alkoxy andC1-C16 haloalkyl; and n and m are each, independently, integers from 1to
 500. 16. The method of claim 14, wherein the at least onepolycarbonate macrodiol includes at least one poly(alkylene carbonate).17. The method of claim 14, wherein the chain extender includes at leastone member of the group consisting of 1,4-butanediol; 1,5-pentanediol;1,6-hexanediol; 1,8-octanediol; 1,9-nonanediol; 1,10-decanediol,1,12-dodecanediol; 1,4-cyclohexane dimethanol; p-xyleneglycol and1,4-bis(2-hydroxyethoxy) benzene.
 18. The method of claim 14, whereinthe chain extender includes at least one member of the group consistingof 1,4-diaminobutane; 1,5-diaminopentane; 1,6-diaminohexane;1,8-diaminooctane; 1,9-diaminononane; 1,10-diamonodecane,1,12-diaminododacane; 1,4-diaminocyclohexane; 2,5-diaminoxylene andisophoronediamine and water.
 19. The method of claim 14, wherein the atleast one polycarbonate macrodiol is in an amount of 10% to 30% byweight of the soft segment, and the at least one of the polyisobutylenemacrodiol and the polyisobutylene diamine is in an amount of 70% to 90%by weight of the soft segment.
 20. The method of claim 14, wherein theat least one of the polyisobutylene macrodiol and the polyisobutylenediamine is a polyisobutylene macrodiol and the number average molecularweight of the polyisobutylene macrodiol is about 400 Da to about 6000Da.